Conformational Changes Research Articles

PARP1 inhibition prevents oxidative stress in age-related hearing loss via PAR-Ca2+-AIF axis in cochlear strial marginal cells

Studies have highlighted oxidative damage in the inner ear as a critical pathological basis for sensorineural hearing loss, especially the presbycusis. Poly(ADP-ribose) polymerase-1 (PARP1) activation responds to oxidative stress-induced DNA damage with pro-repair and pro-death effects resembling two sides of the same coin. PARP1-related cell death, known as parthanatos, whose underlying mechanisms are attractive research hotspots but remain to be clarified. In this study, we observed that aged rats showed stria vascularis degeneration and oxidative damage, and PARP1-dependent cell death was prominent in age-related cochlear disorganization and dysfunction. Based on oxidative stress model of primary cultured stria marginal cells (MCs), we revealed that upregulated PARP1 and PAR (Poly(ADP-ribose)) polymers are responsible for MCs oxidative death with high mitochondrial permeability transition pore (mPTP) opening and mitochondrial membrane potential (MMP) collapse, while inhibition of PARP1 ameliorated the adverse outcomes. Importantly, the PARylation of apoptosis-inducing factor (AIF) is essential for its conformational change and translocation, which subsequently causes DNA break and cell death. Concretely, the interaction of PAR and truncated AIF (tAIF) is the mainstream in the parthanatos pathway. We also found that the effects of AIF cleavage and release were achieved through calpain activity and mPTP opening, both of which could be regulated by PARP1 via mediation of mitochondria Ca2+ concentration. In conclusion, the PAR-Ca2+-tAIF signaling pathway in parthanatos contributes to the oxidative stress damage observed in MCs. Targeting PAR-Ca2+-tAIF might be a potential therapeutic strategy for the early intervention of presbycusis and other oxidative stress-associated sensorineural deafness.

In vitro susceptibility of grass carp fish (Ctenopharyngodon idella) to oxidized myosin on structural change of protein secondary structure associated with reactive oxygen species (ROS) treatment

This study aimed to investigate the in vitro susceptibility of grass carp (Ctenopharyngodon idella) oxidized myosin, with the treatment of H2O2 levels being 0, 25, 50, and 100 μmol/L, respectively. The results showed that in vitro oxidation of myosin, reactive oxidative species promoted protein modifications that propagated the conformation changes on myosin secondary structure, leading to a significant increase (P < 0.05) in the protein carbonyl content in the high oxidation treatment, when compared to the low and medium treatments. The results of the Western blot analysis and sodium-polyacrylamide amide-dodecyl sulfate gel electrophoresis demonstrated that in vitro oxidation actively promoted the degradation of protein molecular weight and Desmin (53 kDa) deterioration in the sample with the highest concentration treatment of H2O2. Circular dichroism spectra showed a decrease in α-helix content from 70.1% to 29.8% and an increase in β-sheet percentage from 5.6% to 17.4%. Meanwhile, cysteine and methionine as the free amino acids were most susceptible to oxidative change due to their high sensitivity to the reaction of the sulfur group of amino acids. Protein degradation induced by oxidation resulted in significant changes to the protein secondary structure, as evidenced by the observation of oxidized myosin under different H2O2 levels.

Unveiling the transition of tumbling and tank-treading dynamics of star-shaped polyelectrolytes in shear flow by modulating the solution's dielectric properties.

The effects of the solution's dielectric properties on the conformation and dynamics of star-shaped polyelectrolytes in shear flow are investigated using a hybrid simulation method coupling multi-particle collision dynamics and molecular dynamics. The simulation results showed that by modulating the dielectric properties of the solution, star-shaped polyelectrolytes showed a three-step dynamic behavior transition from tumbling to tank-treading to tumbling dynamics under shear flow. The analysis indicated that this distinct transition in dynamics could be attributed to the uneven distribution of counterions induced by shear on the chain, resulting in a change in the polyelectrolyte conformation and degree of segmental alignment in arms. These findings contribute to a comprehensive understanding of the non-equilibrium dynamics of star-shaped polyelectrolytes in shear flow and offer a viable approach for controlling the dynamic behavior of star-shaped polyelectrolytes by adjusting the dielectric properties of the solution.

Stimulus-Induced Dynamic Behavior Regulation of Flexible Crystals through the Tuning of Module Rigidity.

Introducing dynamic behavior into periodic frameworks has borne fruit in the form of flexible porous crystals. The detailed molecular design of frameworks in order to control their collective dynamics is of particular interest, for example, to achieve stimulus-induced behavior. Herein, by varying the degree of rigidity of ditopic pillar linkers, two isostructural flexible metal-organic frameworks (MOFs) with common rigid supermolecular building bilayers were constructed. The subtle substitution of single (in bibenzyl-4,4'-dicarboxylic acid; H2BBDC) with double (in 4,4'-stilbenedicarboxylic acid; H2SDC) C-C bonds in pillared linkers led to markedly different flexible behavior of these two MOFs. Upon the removal of guest molecules, both frameworks clearly show reversible single-crystal-to-single-crystal transformations involving the cis-trans conformation change and a resulting swing of the corresponding pillar linkers, which gives rise to Flex-Cd-MOF-1a and Flex-Cd-MOF-2a, respectively. Strikingly, a more favorable gas-induced dynamic behavior in Flex-Cd-MOF-2a was verified in detail by stepwise C3H6/C3H8 sorption isotherms and the corresponding in situ powder X-ray diffraction experiments. These insights are strongly supported by molecular modeling studies on the sorption mechanism that explores the sorption landscape. Furthermore, a consistency between the macroscopic elasticity and microscopic flexibility of Flex-Cd-MOF-2 was observed. This work fuels a growing interest in developing MOFs with desired chemomechanical functions and presents detailed insights into the origins of flexible MOFs.

Impact of protein conformations on binding free energy calculations in the beta-secretase 1 system.

In binding free energy calculations, simulations must sample all relevant conformations of the system in order to obtain unbiased results. For instance, different ligands can bind to different metastable states of a protein, and if these protein conformational changes are not sampled in relative binding free energy calculations, the contribution of these states to binding is not accounted for and thus calculated binding free energies are inaccurate. In this work, we investigate the impact of different beta-sectretase 1 (BACE1) protein conformations obtained from x-ray crystallography on the binding of BACE1 inhibitors. We highlight how these conformational changes are not adequately sampled in typical molecular dynamics simulations. Furthermore, we show that insufficient sampling of relevant conformations induces substantial error in relative binding free energy calculations, as judged by a variation in calculated relative binding free energies up to 2kcal/mol depending on the starting protein conformation. These results emphasize the importance of protein conformational sampling and pose this BACE1 system as a challenge case for further method development in the area of enhanced protein conformational sampling, either in combination with binding calculations or as an endpoint correction.

Molecular Dynamics Simulations of the Mutated Proton-Transferring a-Subunit of E. coli FoF1-ATP Synthase.

The membrane Fo factor of ATP synthase is highly sensitive to mutations in the proton half-channel leading to the functional blocking of the entire protein. To identify functionally important amino acids for the proton transport, we performed molecular dynamic simulations on the selected mutants of the membrane part of the bacterial FoF1-ATP synthase embedded in a native lipid bilayer: there were nine different mutations of a-subunit residues (aE219, aH245, aN214, aQ252) in the inlet half-channel. The structure proved to be stable to these mutations, although some of them (aH245Y and aQ252L) resulted in minor conformational changes. aH245 and aN214 were crucial for proton transport as they directly facilitated H+ transfer. The substitutions with nonpolar amino acids disrupted the transfer chain and water molecules or neighboring polar side chains could not replace them effectively. aE219 and aQ252 appeared not to be determinative for proton translocation, since an alternative pathway involving a chain of water molecules could compensate the ability of H+ transmembrane movement when they were substituted. Thus, mutations of conserved polar residues significantly affected hydration levels, leading to drastic changes in the occupancy and capacity of the structural water molecule clusters (W1-W3), up to their complete disappearance and consequently to the proton transfer chain disruption.

Nonalternant Nanographenes Containing N-Centered Cyclopenta[ef]heptalene and Aza[7]Helicene Units.

Introducing helical subunits into negatively curved π-systems has a significant effect on both the molecular geometry and photophysical properties; however, the synthesis of these helical π-systems embedded with nonbenzenoid subunits remains challenging due to the high strain deriving from both the curvature and helix. Here, we report a family of nonalternant nanographenes containing a nitrogen (N)-doped cyclopenta[ef]heptalene unit. Among them, CPH-2 and CPH-3 can be viewed as hybrids of benzoannulated cyclopenta[ef]heptalene and aza[7]helicene. The crystal structures revealed a saddle geometry for CPH-1, a saddle-helix hybrid for CPH-2, and a twist-helix hybrid for CPH-3. Experimental measurements and theoretical calculations indicate that the saddle moieties in CPHs undergo flexible conformational changes at room temperature, while the aza[7]helicene subunit exhibits a dramatically increased racemization energy barrier (78.2 kcal mol-1 for CPH-2, 143.2 kcal mol-1 for CPH-3). The combination of the nitrogen lone electron pairs of the N-doped cyclopenta[ef]heptalene unit with the twisted helix fragments results in rich photophysics with distinctive fluorescence and phosphorescence in CPH-1 and CPH-2 and the similar energy fluorescence and phosphorescence in CPH-3. Both enantiopure CPH-2 and CPH-3 display distinct circular dichroism (CD) signals in the UV-vis range. Notably, compared to the reported fully π-extended helical nanographenes, CPH-3 exhibits excellent chiroptical properties with a |gabs| value of 1.0 × 10-2 and a |glum| value of 7.0 × 10-3; these values are among the highest for helical nanographenes.

Skipping events impose repeated binding attempts: profound kinetic implications of protein-DNA conformational changes.

The kinetics of protein-DNA recognition, along with its thermodynamic properties, including affinity and specificity, play a central role in shaping biological function. Protein-DNA recognition kinetics are characterized by two key elements: the time taken to locate the target site amid various nonspecific alternatives; and the kinetics involved in the recognition process, which may necessitate overcoming an energetic barrier. In this study, we developed a coarse-grained (CG) model to investigate interactions between a transcription factor called the sex-determining region Y (SRY) protein and DNA, in order to probe how DNA conformational changes affect SRY-DNA recognition and binding kinetics. We find that, not only does a requirement for such a conformational DNA transition correspond to a higher energetic barrier for binding and therefore slower kinetics, it may further impede the recognition kinetics by increasing unsuccessful binding events (skipping events) where the protein partially binds its DNA target site but fails to form the specific protein-DNA complex. Such skipping events impose the need for additional cycles protein search of nonspecific DNA sites, thus significantly extending the overall recognition time. Our results highlight a trade-off between the speed with which the protein scans nonspecific DNA and the rate at which the protein recognizes its specific target site. Finally, we examine molecular approaches potentially adopted by natural systems to enhance protein-DNA recognition despite its intrinsically slow kinetics.

Mechanistic basis of the dynamic response of TWIK1 ionic selectivity to pH

Highly selective for K+ at neutral pH, the TWIK1 channel becomes permeable to Na+ upon acidification. Using molecular dynamics simulations, we identify a network of residues involved in this unique property. Between the open and closed states previously observed by electron microscopy, molecular dynamics simulations show that the channel undergoes conformational changes between pH 7.5–6 involving residues His122, Glu235, Lys246 and Phe109. A complex network of interactions surrounding the selectivity filter at high pH transforms into a simple set of stronger interactions at low pH. In particular, His122 protonated by acidification moves away from Lys246 and engages in a salt bridge with Glu235. In addition, stacking interactions between Phe109 and His122, which stabilize the selectivity filter in its K+-selective state at high pH, disappear upon acidification. This leads to dissociation of the Phe109 aromatic side chain from this network, resulting in the Na+-permeable conformation of the channel.

α-Hydrazino Acid Insertion Governs Peptide Organization in Solution by Local Structure Ordering.

In this work, we have applied the concept of α-hydrazino acid insertion in a peptide sequence as a means of structurally organizing a potential protein-protein interactions (PPI) inhibitor. Hydrazino peptides characterized by the incorporation of an α-hydrazino acid at specific positions introduce an additional nitrogen atom into their backbone. This modification leads to a change in the electrostatic properties of the peptide and induces the restructuring of its hydrogen bonding network, resulting in conformational changes toward more stable structural motifs. Despite the successful use of synthetic hydrazino oligomers in binding to nucleic acids, the structural changes due to the incorporation of α-hydrazino acid into short natural peptides in solution are still poorly understood. Based on NMR data, we report structural models of p53-derived hydrazino peptides with elements of localized peptide structuring in the form of an α-, β-, or γ-turn as a result of hydrazino modification in the peptide backbone. The modifications could potentially lead to the preorganization of a helical secondary peptide structure in a solution that is favorable for binding to a biological receptor. Spectroscopically, we observed that the ensemble averaged rapidly interconverting conformations, including isomerization of the E-Z hydrazide bond. This further increases the adaptability by expanding the conformational space of hydrazine peptides as potential protein-protein interaction antagonists.

Hybrid Small-Molecule/Protein Fluorescent Probes.

Hybrid small-molecule/protein fluorescent probes are powerful tools for visualizing protein localization and function in living cells. These hybrid probes are constructed by diverse site-specific chemical protein labeling approaches through chemical reactions to exogenous peptide/small protein tags, enzymatic post-translational modifications, bioorthogonal reactions for genetically incorporated unnatural amino acids, and ligand-directed chemical reactions. The hybrid small-molecule/protein fluorescent probes are employed for imaging protein trafficking, conformational changes, and bioanalytes surrounding proteins. In addition, fluorescent hybrid probes facilitate visualization of protein dynamics at the single-molecule level and the defined structure with super-resolution imaging. In this review, we discuss development and the bioimaging applications of fluorescent probes based on small-molecule/protein hybrids.

Significance of Zn2+ in RyR1 for Structural Integrity and Ligand Binding: Insight from Molecular Dynamics.

Ryanodine receptor type 1 (RyR1) is a Ca2+-release channel central to skeletal muscle excitation-contraction (EC) coupling. RyR1's cryo-EM structures reveal a zinc-finger motif positioned within the cytoplasmic C-terminal domain (CTD). Yet, owing to limitations in cryo-EM resolution, RyR1 structures lack precision in detailing the metal coordination structure, prompting the need for an accurate model. In this study, we employed molecular dynamics (MD) simulations and the density functional theory (DFT) method to refine the binding characteristics of Zn2+ in the zinc-finger site of the RyR1 channel. Our findings also highlight substantial conformational changes in simulations conducted in the absence of Zn2+. Notably, we observed a loss of contact at the interface between protein domains proximal to the zinc-finger site, indicating a crucial role of Zn2+ in maintaining structural integrity and interdomain interactions within RyR1. Furthermore, this study provides valuable insights into the modulation of ATP, Ca2+, and caffeine binding, shedding light on the intricate relationship between Zn2+ coordination and the dynamic behavior of RyR1. Our integrative approach combining MD simulations and DFT calculations enhances our understanding of the molecular mechanisms governing ligand binding in RyR1.

Electrochemical aptasensor for ultrasensitive cadmium detection through hybridization chain-amplified reaction

Detection of cadmium ion (Cd2+) is of great necessity in safeguarding public health by providing accurate information about its presence in food matrices. A signal amplification electrochemical biosensor system with DNA cascade reaction was designed for ultrasensitive determination of Cd2+, in which in-situ synthesized Ag nanoclusters (Ag NCs) were identified as signal reporters. The highly conductive electrode with large active area, produced by gold deposition on the screen-printed electrodes (SPE), was regarded as an electrochemical platform. Cd2+ aptamer (Apt) was immobilized on the Au NPs modified SPE (Au-SPE) through the Au-S bound to capture Cd2+ by conformational change. Meanwhile, the unoccupied Apt was able to be paired with H1 and H2 by base complementation to accelerate the hybridization chain reaction (HCR) cascade, and the in-situ synthesis of Ag NCs on cytosine-rich sequence of H1 to achieve the quantification of Cd2+ according to the linear sweep voltammetry (LSV). The constructed electrochemical aptasensor exhibited a linear range from 0.1 ng/mL to 100 ng/mL, and the detection limit was 0.088 ng/mL for Cd2+ under optimal conditions. This HCR-based electrochemical aptasensor allowed practical application to tea and vegetable samples with satisfactory accuracy, confirming its promising application for rapid detection of targets in complex systems. Therefore, this platform holds promise for the rapid detection of heavy metals.

Cadmium binding by the F-box domain induces p97-mediated SCF complex disassembly to activate stress response programs

The F-box domain is a highly conserved structural motif that defines the largest class of ubiquitin ligases, Skp1/Cullin1/F-box protein (SCF) complexes. The only known function of the F-box motif is to form the protein interaction surface with Skp1. Here we show that the F-box domain can function as an environmental sensor. We demonstrate that the F-box domain of Met30 is a cadmium sensor that blocks the activity of the SCFMet30 ubiquitin ligase during cadmium stress. Several highly conserved cysteine residues within the Met30 F-box contribute to binding of cadmium with a KD of 8 µM. Binding induces a conformational change that allows for Met30 autoubiquitylation, which in turn leads to recruitment of the segregase Cdc48/p97/VCP followed by active SCFMet30 disassembly. The resulting inactivation of SCFMet30 protects cells from cadmium stress. Our results show that F-box domains participate in regulation of SCF ligases beyond formation of the Skp1 binding interface.

Molecular structure and selective theophylline complexation by conformational change of diethyl N,N'-(1,3-phenylene)dicarbamate.

The receptor ability of diethyl N,N'-(1,3-phenylene)dicarbamate (1) to form host-guest complexes with theophylline (TEO) and caffeine (CAF) by mechanochemistry was evaluated. The formation of the 1-TEO complex (C12H16N2O4·C7H8N4O2) was preferred and involves the conformational change of one of the ethyl carbamate groups of 1 from the endo conformation to the exo conformation to allow the formation of intermolecular interactions. The formation of an N-H...O=C hydrogen bond between 1 and TEO triggers the conformational change of 1. CAF molecules are unable to form an N-H...O=C hydrogen bond with 1, making the conformational change and, therefore, the formation of the complex impossible. Conformational change and selective binding were monitored by IR spectroscopy, solid-state 13C nuclear magnetic resonance and single-crystal X-ray diffraction. The 1-TEO complex was characterized by IR spectroscopy, solid-state 13C nuclear magnetic resonance, powder X-ray diffraction and single-crystal X-ray diffraction.

Exploring the effect of corn starch/pea protein blending on the physicochemical and structural properties of biopolymer films and their aging resistance

This study investigated the potential effect of blending corn starch and pea protein isolate in various ratios (100:0, 70:30, 50:50, 30:70, and 0:100) on the aging properties of biodegradable films. Unlike previous research, the focus was on the often-overlooked aspect of film aging. Fourier-transform infrared spectroscopy and X-ray diffraction demonstrated the physical blending of corn starch and pea protein, along with chemical bonding and conformational changes. The optical and microstructural properties showed the formation of smooth, homogeneous films with good compatibility between the polymers. The water resistance, barrier, and mechanical properties corresponding to the intrinsic nature of protein polymers showed a minimized fluctuations in film properties as film ages, with a reduction of at least twice when protein is added. Remarkably, the blend with a ratio of 30:70 demonstrated the most stable properties during aging. These results demonstrated that blending the pea protein isolate was favorable for delaying the retrogradation and recrystallization of corn starch films. Understanding how these blends influence the aging characteristics of films is not only a novel contribution to the scientific community but also holds practical significance, potentially opening a potential for applications in various industries.

Dynamics of interdomain rotation facilitates FtsZ filament assembly

FtsZ, the tubulin homolog essential for bacterial cell division, assembles as Z-ring at the division site, and directs peptidoglycan synthesis by treadmilling. It is unclear how FtsZ achieves its kinetic polarity that drives treadmilling. To obtain insights into fundamental features of FtsZ assembly dynamics independent of peptidoglycan synthesis, we carried out the structural and biochemical characterization of FtsZ from the cell wall-less bacteria, Spiroplasma melliferum (SmFtsZ). Interestingly the structures of SmFtsZ, determined in GDP and GMPPNP bound form, were captured as domain swapped dimers. SmFtsZ was found to be a slower GTPase and has higher critical concentration (CC) for polymerization compared to Escherichia coli FtsZ (EcFtsZ). In FtsZs, a conformational switch from R-state (close) to T-state (open) favors polymerization. We identified a residue, Phe224, located at the interdomain cleft of SmFtsZ, which is crucial for R- to T-state transition. The mutation F224M in SmFtsZ cleft resulted in higher GTPase activity and lower CC, whereas the corresponding M225F in EcFtsZ resulted in cell division defects in E. coli. Our results demonstrate that relative rotation of the domains is a rate-limiting step of polymerization and that the dynamics of the interdomain rotation is important for the assembly of FtsZ filament. Our structural analysis of interdomain interactions suggests that this step is plausibly triggered upon addition of a GTP-bound monomer to the filament through interaction of the preformed N-terminal domain (NTD). Hence, the addition of monomers to the NTD-exposed end of filament is slower in comparison to the C-terminal domain (CTD) end, thus explaining kinetic polarity. In summary, the study sheds light on the molecular mechanisms underlying FtsZ assembly dynamics and highlights the importance of interdomain interactions, conformational changes, and specific residues in regulating FtsZ polymerization, which are crucial for bacterial cell division.

Effects of different protein cross-linking degrees on physicochemical and subsequent thermal gelling properties of silver carp myofibrillar proteins sol subjected to freeze-thaw cycles

Knowledge regarding the denaturation process and control methods for depolymerized sol-state myofibrillar proteins (MPs) during freezing remains scant. This study investigated the effects of protein cross-linking treatment before freezing on physicochemical and subsequent gelation properties of MPs sol subjected to freeze-thaw (F-T) cycles. Results indicated that after five F-T cycles, cross-linked MPs sols showed increased high molecular weight polymers and bound water (T21a and T21b) mobility, suggesting enhanced protein-protein interactions at the expense of protein-water interactions. Upon heating after F-T cycles, gels formed from cross-linked sols exhibited significantly higher hardness, springiness, and cooking loss (P < 0.05), alongside more contracted gel networks. Correlation analysis revealed that the formation and properties of thermal gel after freezing closely relate to changes in molecular conformation and chemical bonds of cross-linked MPs sol during freezing. This study provides new insights into regulating the freezing stability and post-thawed thermal processing properties of sol-based surimi products.

Potential Effect of Chloroquine in Modulating Hyperglycemia and PTEN Receptor Linked Dyslipidemia on Alloxan-induced Diabetic Mice

Background: Diabetes mellitus is a life-threatening disease associated with worsening of glycemic control, progressive metabolic dysfunctions and disruption of the Phosphatase and Tensin Homolog (PTEN) receptor. Purpose: To evaluate the effect of chloroquine on blood glucose level and lipid profile of alloxan-induced diabetic mice and to observe its interaction with PTEN, a negative regulator of insulin signaling pathway. Methodology: Thirty mice were used for the experiment. A group (n = 5) was kept as healthy control while the others were pre-treated with 140 mg/kg of alloxan monohydrate in distilled water. The alloxan-induced diabetic mice were randomly divided into four groups: diabetic model control group, 60 mg/kg chloroquine, 120 mg/kg chloroquine, and 10 mg/kg glibenclamide treatment groups respectively. Treatment was done once daily for seven days and the blood glucose level was investigated acutely and then daily throughout the experimental period. A molecular docking study was also conducted to evaluate the interaction of chloroquine with PTEN using PYRX software, while an automated COBAS C 311 machine was used to analyze the lipid profile after the treatment period. Results: Oral administration of chloroquine gradually and significantly lowered the raised blood glucose level in a time- and dose-dependent manner. A repeated study with 120 mg/kg of chloroquine revealed a decline in blood sugar from 221.5 ± 3.6 on day 1 to 85.5 ± 2.4 on day 7 in comparison to glibenclamide, whose sugar level was reduced to 75.5 ± 3.7 at the end of day 7. The docking study revealed a non-competitive inhibition with an inhibition score of -6.1 in comparison to metformin, which had a score of -4.4, and glibenclamide, which had a score of -9.0. This interaction resulted in a conformational change of the receptor, hence, enhancing glucose uptake and reducing the raised hyperglycemia. Treatment with chloroquine was also observed to reduce the total cholesterol and triglyceride levels from 162 in the model group to 144 and 141 to 116 mmol/L, respectively. The levels of low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein (VLDL) following treatment with chloroquine were not statistically different from the non-diabetic healthy mice. These values were very similar to those obtained with glibenclamide-treated diabetic mice. Conclusion: From the results, chloroquine possesses potent antidiabetic properties and can improve dyslipidemia imposed by hyperglycemia probably owing to its inhibition of PTEN, a negative regulator of insulin resistance.

BCM-7: Opioid-like Peptide with Potential Role in Disease Mechanisms.

Bovine milk is an essential supplement due to its rich energy- and nutrient-rich qualities. Caseins constitute the vast majority of the proteins in milk. Among these, β-casein comprises around 37% of all caseins, and it is an important type of casein with several different variants. The A1 and A2 variants of β-casein are the most researched genotypes due to the changes in their composition. It is accepted that the A2 variant is ancestral, while a point mutation in the 67th amino acid created the A1 variant. The digestion derived of both A1 and A2 milk is BCM-7. Digestion of A2 milk in the human intestine also forms BCM-9 peptide molecule. The opioid-like characteristics of BCM-7 are highlighted for their potential triggering effect on several diseases. Most research has been focused on gastrointestinal-related diseases; however other metabolic and nervous system-based diseases are also potentially triggered. By manipulating the mechanisms of these diseases, BCM-7 can induce certain situations, such as conformational changes, reduction in protein activity, and the creation of undesired activity in the biological system. Furthermore, the genotype of casein can also play a role in bone health, such as altering fracture rates, and calcium contents can change the characteristics of dietary products. The context between opioid molecules and BCM-7 points to a potential triggering mechanism for the central nervous system and other metabolic diseases discussed.