Great Physiological Importance Research Articles

Hypothalamic noradrenaline synthesis, uptake and storage in rats during adaptation to long-term individual housing

The brain monoamine systems play a crucial role in mediating social behaviors. In order to assess the effect of socially isolated rats on neurochemical substrates in hypothalamus we measured levels of tyrosine hydroxylase (TH), noradrenaline transporter (NET) and vesicular monoamine transporter 2 (VMAT 2). Our results show that 12 weeks of social isolation produced no significant changes in noradrenaline content in hypothalamus. The levels of TH and NET were elevated in these animals, whereas level of VMAT 2 was unchanged. The data suggests that both enhanced synthesis and reuptake may aid in the recovery of noradrenaline content in the hypothalamus. The adaptation of the hypothalamic noradrenaline to long period of stress may have great physiological importance and may represent mechanism designed to help the organism adapt to the deleterious effects of chronic indiviual housing.

Halogenated phospholipids regulate secretory phospholipase A2 group IIA activity

Secretory phospholipase A2 group IIA (sPLA2-IIA) is an active participant of inflammation. The enzyme destroys bacterial cell wall and induces production of biologically active lipid mediators. It is involved in various pathological processes and high serum content and activity of sPLA2-IIA are associated with adverse cardiovascular events. Study of sPLA2-IIA regulation is of great physiological and clinical importance and is necessary for better understanding of mechanisms underlying inflammation. Another major participant of inflammatory response is the enzyme myeloperoxidase (MPO) which is secreted by neutrophils in the focus of inflammation and catalyzes formation of HOCl and HOBr. Both halogenated (chloro- and bromohydrins) and oxidized lipids are formed due to interaction between HOCl and HOBr with unsaturated bonds of phospholipid acyl chains. Previously we showed that oxidized phospholipids stimulate sPLA2-IIA activity. In this study we examined the effects of chloro- and bromohydrins of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) on sPLA2-IIA activity.In contrast to POPC, chloro- and bromohydrins of POPC (POPC-Cl and POPC-Br, respectively) were not hydrolyzed by sPLA2-IIA. In addition, phospholipids which are sPLA2-IIA substrates, were not cleaved by the enzyme in the presence of POPC-Cl and POPC-Br. Halogenohydrins of POPC prevented the activity of both purified and serum sPLA2-IIA. Blocking effects of POPC-Cl and POPC-Br were abolished by increased concentrations of phospholipid-substrate.These results suggest that halogenated phospholipids formed in MPO-dependent reactions can be considered as a new class of biologically active compounds potentially capable of regulating sPLA2-IIA activity in the areas of inflammation and producing the effects opposite to those of oxidized phospholipids. Control over sPLA2-IIA can be useful in the therapy of diseases involving systemic inflammation.

Cysteine-modulated colorimetric sensing of extracellular Mg2+ in rat brain based on the strong chelation interaction between dithiothreitol and Mg2+

Simple and effective measurement of Mg(2+) in the brain of living animals is of great physiological and pathological importance. In this study, we report a facile yet highly selective colorimetric method for effective sensing of cerebral Mg(2+). The method is based on rational design of surface chemistry of gold nanoparticles (Au-NPs) with functional molecules including 1,4-dithiothreitol (DTT) and cysteine, enabling the fine tuning of the surface chemistry of Au-NPs in such a way that the addition of Mg(2+) into the Au-NPs dispersion could selectively trigger the change of the dispersion/aggregation states of Au-NPs. The strong chelation interaction between Mg(2+) and the hydroxyls in 1,4-dithiothreitol and the co-existence of cysteine on the surface of Au-NPs could, on one hand, enable the selective colorimetric detection of Mg(2+) and, on the other hand, avoid the aggregation of Au-NPs induced by DTT itself. As a result, the addition of Mg(2+) into the dispersion of the Au-NPs containing both cysteine and DTT results in the changes in both the color and the UV-vis spectra of the Au-NPs dispersion. The signal readout shows a linear relationship of Mg(2+) within the concentration range from 1 μM to 40 μM with a detection limit of 800 nM (S/N = 3). Moreover, the assay demonstrated here is free from the interference of some physiological species commonly existing in rat brain. Although Ca(2+) could interfere with the detection of Mg(2+) because of its strong chelation with DTT, it could be selectively masked by masking agent (i.e., ethyleneglcol-bis (2-aminoethylether) tetraacetic acid). By combining the microdialysis technique, the basal dialysate level of Mg(2+) is determined to be 299.2 ± 41.1 μM (n = 3) in the cerebral systems. The method essentially offers a new method for the detection of Mg(2+) in the cerebral system.

Hypothesis review: The direct interaction of food nanoparticles with the lymphatic system

Besides digestion and assimilation, there are other modes of direct interaction between food and human body. As it is known, the mucosal layer of the digestive tract interfaces with food after the digestion process. It has been demonstrated to uptake the micro- and nanoparticles via mucosa-associated lymphatic tissues (MALT). On the other hand, food is a typical polydisperse system and contains micro- and nanoparticles with different sizes and properties. Accordingly, it is hypothesized that food nanoparticles can directly interact with MALT and more specifically with the support of the preliminary experimental data from our research, that antioxidant nanoparticles can interact with the lymphatic vessels. This kind of interaction would be of great physiological importance. The confirmation of the hypothesis will establish a significant and novel approach to understand food system and provide answers to currently incomprehensible phenomena such as the biological functions of phytochemicals with low bioavailability.

Human Heart by Art

Heart is of great importance in maintaining the life of the body. Enough to stop working for a few minutes to cause death, and hence the great importance in physiology, medicine, and research. This fact was already emphasized in the Bible in the Book of Proverbs, chapter 4 verse 23: "Keep your heart with all diligence, for out of it is the wellspring of life." Art was able to demonstrate the heart from various aspects; realistically, as done by Leonardo de Vinci who demonstrated the halves of the heart and its blood vessels. Symbolically, as a source of life, the heart was demonstrated by the artist Mrs. Erlondeiel, as a caricature by Salvador Dali, as an open heart by Sawaya, etc. Finally, it should be emphasized that different demonstrations of the human heart by many artworks make this most important organ of our body (that cannot be seen from outside) more familiar and clearer to us. And this is the purpose of this article-to demonstrate the heart through a large number of artworks of different kinds.

Functional analysis of leukemia inhibitory factor in osteoblast differentiation of bone marrow stromal cells

Functional analysis of leukemia inhibitory factor in osteoblast differentiation of bone marrow stromal cells

Bone material properties in hypoparathyroidism

Bone material properties in hypoparathyroidism

The interactive effects of selenomethionine and methylmercury on their absorption, disposition, and elimination in juvenile white sturgeon

Selenium (Se) and mercury (Hg) are prevalent pollutants of industrialized watersheds. However, when co-administered, Se has protective effects on organisms from Hg. The mechanism is not fully understood, but it is thought that Se reduces Hg availability, either by forming biologically inert complexes and/or associating with selenoproteins. Despite concerns with aquatic contaminations, relatively little information is available on the interaction in aquatic organisms. In the present study, the interactive effects of Se and Hg on their absorption, disposition, and elimination were examined in juvenile white sturgeon, a benthic fish species at high risk to exposures of both contaminants. Selenium and Hg were provided as l-selenomethionine (SeMet) and methylmercury (MeHg), respectively. Groups of 10 sturgeon were orally intubated with a single dose of either 0 (control), SeMet (500μg Se/kg body weight; BW), MeHg (850μg Hg/kg BW), or their combination (Se/Hg; 500μg Se/kg and 850μg Hg/kg BW). The blood was repeatedly sampled and urine collected from the fish, over a 48h post intubation period. At 48h, the fish were sacrificed for Se and Hg tissue concentration and distribution. The co-administration of SeMet and MeHg significantly (p<0.05) lowered blood concentrations of both Se and Hg and tissue Se concentrations. Similarly, assimilation of Se and Hg was also reduced significantly. The interaction has a more quantitative effect on Se metabolism because the reduction in the overall tissue Se is a consequence of reduced Se absorption at the gut and not from the metabolic effects after absorption. In contrast, given the pulse increase in blood Hg concentration, tissue redistribution, and increased urinary elimination, the interactive effect on tissue Hg concentration is likely to be post-absorption. Even in the absence of exogenous SeMet, Se and Hg co-accumulated in tissue at a Se:Hg molar ratio greater than 1. Thus, similar to mammals, maintaining at least a 1:1 molar ratio of Se and Hg is of great physiological importance in the white sturgeon. Interestingly, SeMet did not divert Hg from the brain. Allocation of Se from the kidneys may have occurred in order to maintain the high Se:Hg molar ratios in the brain of white sturgeon. In the current study, the combined use of kinetic analysis and that of the conventional approach of measuring tissue concentration changes provided a comprehensive understanding of the interactive effect of SeMet and MeHg on their respective metabolic processes in juvenile white sturgeon.

Continuous Electrochemical Monitoring of Extracellular Lactate Production from Neonatal Rat Cardiomyocytes following Myocardial Hypoxia

Continuous monitoring of lactate production from cardiomyocytes is of great physiological and pathological importance since the level of lactate in extracellular fluid is closely associated with myocardial energy metabolism with implication in the diagnosis and therapeutics of myocardial hypoxia and ischemia. This study demonstrates an electrochemical approach to continuous monitoring of lactate production from neonatal rat cardiomyocytes following myocardial hypoxia with a dehydrogenase-based electrochemical biosensor and a negative pressure driven culture sampling. To eliminate the effect of pH variation occurring following the cardiomyocyte hypoxia on the biosensor response and to supply nicotinamide adenine dinucleotide (NAD(+)) cofactor necessary for the enzymatic reaction of lactate dehydrogenase (LDH), artificial cerebrospinal fluid (aCSF) containing NAD(+) cofactor is externally perfused and mixed online with cell culture before the culture goes to the detector. The method exhibits a high selectivity against the electrochemically active species endogenously existing in the extracellular culture of cardiomyocytes and a high tolerance against the variation of pH following cardiomyocyte hypoxia. The dynamic linear range for lactate detection is from 0.20 to 10 mM (I (nA) = 25.6 C(Lactate) (mM) + 20.1, γ = 0.996) with a detection limit of 0.16 mM (S/N = 3). The physiological level of the extracellular lactate of neonatal rat cardiomyocytes is determined to be 1.1 ± 0.1 mM (n = 3) with the cell density of about 0.5 × 10(3) cells/mm(2). When the cardiomyocytes are subject to hypoxia induced with anoxic reagents, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), the extracellular lactate increases to 255 ± 30.3% (n = 3), relative to the physiological level, following 20 min of the hypoxia. This study essentially offers a new and effective electrochemical platform for investigating energy metabolism during cardiac physiological and pathological processes.

DEVELOPMENT, PRESERVATION, AND CHEMICAL AND FATTY ACID PROFILES OF NILE TILAPIA CARCASS MEAL FOR HUMAN FEEDING*

This study evaluated the use of fish processing residues in the preparation of flavored meal from Nile tilapia (Oreochromis niloticus) carcass. Carcasses were washed, labeled, weighed, spice-brined and smoked. After smoking, the carcasses were weighed and ground to a meal. The samples were vacuum packed, labeled and frozen (−18C) until analysis. The prepared meal presented mean moisture, protein, total lipids and ash contents of 17.41, 32.51, 19.72 and 26.22%, respectively. Some fatty acids of great physiological and nutritional importance were found among the 23 fatty acids that were identified, such as alpha-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. The produced meal can be used to enrichment and preparation of several products for human consumption. PRACTICAL APPLICATIONS Nile tilapia carcasses are not commonly used in human feeding, and, most often, they are disposed of. This study was carried out considering the impact of improper disposal of this residue on the environment and seeking suitable technological alternatives for a nobler use of this residue with both economic potential and social application. The prepared meal can be used to enrich school food, as it is a cheap and viable option to food fit for children consumption.

Not being able to see the muscle for the fat

At its simplest, we can express body weight or body composition as comprising of adipose tissue, muscle tissue and skeletal tissue. Body weight and body mass index (BMI) of populations of all ages have been increasing for close to half a century, leading to the present obesity epidemic. The causal pathways linking excessive body fat to serious chronic diseases, including diabetes and heart diseases is now well established. A recent editorial citing body composition data from Li et al. [1] asked the question “Are Normal-Weight Americans Over-Fat?” [2]. This interpretation of the data from Li et al. reinforces an adipocentric view giving adipose tissue primacy; perhaps there is a different view, a sarcocentric view that proposes that people are perhaps becoming under-muscled rather than just over-fat. Data from Canada [3] and Germany [4] indicate that children and adults are getting fatter at the same body weight or BMI. If we are fatter at the same body weight and BMI then the other two tissues, muscle and or bone must be diminishing. Given that this increased body fatness at the same weight is most likely a proxy for decreased physical activity, it is a good bet that muscle is the tissue that has diminished most. The loss of muscle is of great physiological importance as proper-functioning muscle is responsible for most glucose disposal and required to stave off insulin resistance [5, 6]. Proper functioning muscle has been highlighted as important for longevity even after accounting for respiratory fitness and BMI [7]. Therefore it is important to remind those with an adipocentric perspective that a low body fat in itself is not necessarily healthy if it coexists with poor-quality muscle and bone. This is important given various body composition states such as metabolically normal obese individuals [8] and thin persons with significant ectopic fat [9]. We may have better health outcomes if we focus more on the causes and sequelae of body dyscomposition, especially the diminution of muscle mass and function even in the young, rather than assuming the problems of body composition in the general population largely lie in terms of adiposity. The retention and maintenance of muscle and muscle function is coming under increasing scrutiny in our ageing society because of the looming epidemic of sarcopenia and the financial and social impact that this will have. However, the discussion around the diagnosis and prevalence on sarcopenia is centred on the target clinical population, i.e., the elderly [10]. Nevertheless, the data cited above from the USA, Canada and Germany studies highlight that on current form, a number of our children may not meet their genetic potential of muscle mass and by inference muscle function. The medium-term consequences of this muscle shortfall as a risk factor for type 2 diabetes alone is of concern; the longer-term consequences of any muscle shortfall to sarcopenia prevalence and its possible inception at a younger age should be of even greater concern. Those concerned with sarcopenia, including this journal, perhaps need also to focus more on prevention even starting with childhood.

Does PI(4,5)P2 Regulate Voltage-Gated Potassium Channels?

Phosphatidylinositol −4,5-bisphosphate (PI(4,5)P2) is an important regulator of activity of a variety of ion channels including inwardly rectifying potassium channels, KCNQ, TRP, and voltage-gated calcium channels. Several groups have provided evidence that also voltage-gated potassium (Kv) channels might be regulated by PI(4,5)P2. Taking the wide expression of Kv channels in a variety of different tissues into account, such regulation of activity by PI(4,5)P2 could potentially be of great physiological importance. To determine whether several Kv channels show a regulation of their activity by PI(4,5)P2 we have coexpressed them in tsA201-cells with either a voltage-gated lipid 5-phosphatase (VSP), a G-protein coupled receptor (M1R), or an engineered fusion protein carrying both a 4- and 5-lipid phosphatase activity (Pseudojanin, PJ). These tools deplete PI(4,5)P2 with application of depolarization, muscarinic agonists, or rapamycin, respectively. We monitored PI(4,5)P2 amounts at the plasma membrane by FRET with PH-probes from PLCδ1 simultaneously with whole-cell patch-clamp recordings. Activating VSP or PJ inhibited KCNQ2/3 channel current leaving only about 5-10 % remaining current. Activation of M1R inhibited KCNQ2/3 current a comparable amount. Thus the tools used for our assays are working. We tested with them for potential regulation of activity by PI(4,5)P2 of Kv1.1/Kvβ1.1, Kv1.3, Kv1.4 and Kv1.5/Kvβ1.3, Kv3.4, Kv4.2, Kv4.3 (both with different KChIPs and DPP6-s) and HERG/KCNE2. Interestingly, we found a substantial upregulation of current density and a removal of inactivation for Kv1.1/Kvβ1.1 and Kv3.4 upon activation of M1R, but no changes in activity upon only activating VSP or PJ. All other channels tested showed no alteration in activity in any of the assays we used. In conclusion, “physiological” depletion of PI(4,5)P2 at the plasma membrane does not seem to influence activity of most tested Kv channels. Supported by NIH grant NS08174 and the AvH Foundation.

Noninvasive Estimation of Myosin Heavy Chain Composition in Human Skeletal Muscle

Information on muscle fiber type composition is of great importance in muscle physiology and athletic performance. Because there are only a few techniques available that noninvasively and accurately provide an estimate of muscle fiber type composition, the development of additional and alternative approaches is required. Twenty-seven participants (21 men, 6 women) with an average age of 43 ± 18 yr, height of 175 ± 7 cm, and mass of 74 ± 12 kg participated in the study. Delay, contraction, and half relaxation times were calculated from tensiomyographic radial twitch responses of the vastus lateralis muscle. Univariate and multiple linear regression analyses were used to correlate the proportion of myosin heavy chain I (%MHC-I) in a biopsy obtained from the same muscle with a single and all three radial twitch parameters. Delay, contraction, and half relaxation times all correlated with %MHC-I (r = 0.612, 0.878, and 0.669, respectively, at P ≤ 0.001). When all three parameters were included in a multiple linear regression, the correlation with the %MHC-I was even better (R = 0.933, P < 0.001). These data suggest that time parameters of the skeletal muscle mechanical radial twitch response, measured with a contact linear displacement sensor, can be used as an accurate noninvasive predictor of the %MHC-I in a muscle.

Application of Gaussian Network Model to Elucidate Functional Modes of Motion in a Glutamate Transporter

Glutamate transporters located on the plasma membrane of glia and neurons are responsible for clearing glutamate from the extracellular space and maintaining its concentration below toxic levels. Disruption in glutamate uptake is associated with acute brain injury (ischemia, stroke, seizures) and chronic pathological conditions, including amyotrophic lateral sclerosis, Hungtington's disease and Alzheimer's disease. Moreover, glutamate transporters possess a substrate-activated chloride current which may regulate neuronal activity. Understanding the mechanism of transport is therefore, of great physiological and medical importance. High resolution structures of a glutamate transporter homolog (GltPh) from an archaeal species were determined recently (Boduker et al, 2007) allowing for establishing a basis for the structural mechanism of binding and transport at the molecular level. We used the Gaussian Network Model (GNM) for protein dynamics to elucidate the most cooperative modes of motions intrinsically accessible to the homotrimer. A concerted opening and closing of the extracellular vestibule is found to be the most dominant mode of motion near the equilibrium structure. This mode of motion is expected to aid in the substrate binding process of the transport machinery. The movement of the extracellular portions of the protein, towards the center of the aqueous cavity is supported by cross-linking experiments with mutants where residues mutated to cysteine are observed to form disulfide bridges with their counterparts in the neighboring subunit. In the X-ray structure, these residues are more than 40 A apart. The formation of these disulfide bridges also results in reduced transport of glutamate, suggesting a functional role for the motion induced by the most cooperative GNM mode.

Sarcoplasmic Reticulum Calcium Content in Normal and Dystrophic Mammalian Skeletal Muscle Fibers

The evaluation of the maximal amount of releasable Ca2+ (Ca2+-content) that is stored in the sarcoplasmic reticulum (SR) of skeletal muscle fibers is a topic of great importance in muscle physiology. We have developed a method to quantitatively estimate the SR Ca2+ content in isolated mammalian muscle fibers based on Ca2+ dependent fluorescence measurements performed in the presence of high concentrations of Ca2+ buffers, and model calculations of Ca2+ flux underlying the fluorescence changes. Single fibers were enzymatically isolated from murine FDB muscles and impaled with two microelectrodes. One electrode, filled with 1M KCl, was used to record the membrane potential throughout the procedure. The other electrode was used to dialyze the fiber with a solution containing either 6-15 mM BAPTA, or up to 60 mM EGTA (pCa=7.0), and adjusted to pH=7.0 with 20 or 60 mM MOPS, respectively. Free myoplasmic Ca2+ concentration ([Ca2+]) changes were measured with the low affinity indicator OGB-5N (200 μM). SR Ca2+ release was elicited by either 20 mM caffeine, or 1 mM 4-chloro-methy-phenol (4CmC), added to the external solution. The maximal fluorescence change of the Ca2+ indicator was assessed at the end of the protocol by exposing the fibers to saponin (0.1 mg/ml in isotonic CaCl2, pH=7.0 with 20 mM MOPS). To prevent changes in shape of the fibers under these conditions, they were pretreated for 1 min with 1% formaldehyde (in Tyrode). The experiments were conducted at 20 °C. A single model compartment was used to estimate (from the [Ca2+] changes) the total Ca2+ released in response to caffeine/4CmC application. We obtained values of SR Ca2+ content in the range of 15-27 mM for normal FDB fibers. Interestingly, comparable values were obtained in fibers from mdx mice.

Permeabilization of baker’s yeast with N-lauroyl sarcosine

N-Lauroyl sarcosine (LS), a cationic, non-toxic and biodegradable detergent readily permeabilized whole cells of baker's yeast (Saccharomyces cerevisiae). Permeabilization was carried out to increase assayable cellular catalase activity, an enzyme of great physiological and industrial importance, and to release 5'-nucleotides which find food/nutritional applications. The event of permeabilization was concentration, time and temperature dependent. Maximum permeabilization of yeast cells were observed when 1 g wet weight (0.2 g dry wt) of cells were permeabilized with 1.0 ml of 2% LS at 45 degrees C for 15 min. LS-permeabilized cells showed 350-fold increase in catalase activity and the supernatant obtained after permeabilization was rich in 5'-nucleotides. LS-permeabilized baker's yeast cells can be used as a source of biocatalyst and to isolate valuable by-products.

Salt-bridge Dynamics Control Substrate-induced Conformational Change in the Membrane Transporter GlpT

Active transport of substrates across cytoplasmic membranes is of great physiological, medical and pharmaceutical importance. The glycerol-3-phosphate (G3P) transporter (GlpT) of the E. coli inner membrane is a secondary active antiporter from the ubiquitous major facilitator superfamily that couples the import of G3P to the efflux of inorganic phosphate (P i) down its concentration gradient. Integrating information from a novel combination of structural, molecular dynamics simulations and biochemical studies, we identify the residues involved directly in binding of substrate to the inward-facing conformation of GlpT, thus defining the structural basis for the substrate-specificity of this transporter. The substrate binding mechanism involves protonation of a histidine residue at the binding site. Furthermore, our data suggest that the formation and breaking of inter- and intradomain salt bridges control the conformational change of the transporter that accompanies substrate translocation across the membrane. The mechanism we propose may be a paradigm for organophosphate:phosphate antiporters.

O selênio no meio ambiente

Normal 0 21 false false false MicrosoftInternetExplorer4 O selênio é conhecido como um elemento de grande importância fisiológica e ecotoxicológica, uma vez que é um micronutriente essencial para a maioria dos organismos, mas também torna-se tóxico em concentrações elevadas. Por esta razão, há um grande interesse em se entender o comportamento deste elemento no meio ambiente. Nesta revisão, alguns aspectos importantes com relação a este elemento são apresentados.

Interaction between vitamin D2 and magnesium in liposomes: Differential scanning calorimetry and FTIR spectroscopy studies

Abstract Magnesium (Mg2+) ion is of great importance in physiology by its intervention in 300 enzymatic systems, its role in membrane structure, its function in neuromuscular excitability and vitamin D metabolism and/or action. In the present study, the interaction of Mg2+, at low (1 mole %) and high (7 mole %) concentrations with dipalmitoyl phosphatidylcholine (DPPC) liposomes has been studied in the presence and absence of vitamin D2 (1 mole %) by using two noninvasive techniques, namely differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. DSC studies reveal that the presence of vitamin D2 in the pure or Mg2+ (at both low and high concentrations) containing liposomes diminishes the pretransition. The calorimetric results also reveal that, inclusion of Mg2+ (more significantly at high concentration) into pure or vitamin D2 containing DPPC liposomes increases the main phase transition temperature. The investigation of the CH2 symmetric, the CH3 asymmetric, the C O stretching, and the PO 2 - antisymmetric double bond stretching bands in FTIR spectra with respect to changes occurring in the wavenumber and/or the bandwidth values as a function of temperature reveal that, inclusion of vitamin D2 or Mg2+ into pure DPPC liposomes orders and decreases the dynamics of the acyl chains in both gel and liquid-crystalline phases and does not induce hydrogen bond formation in the interfacial region. Furthermore, the dynamics of the head groups of the liposomes decreases in both phases. Our findings reveal that, simultaneous presence of vitamin D2 and Mg2+ alters the effect of each other, which is reflected as a decrease in the interactions between these two additives within the model membrane.

Exploration of yeast alkali metal cation/H+ antiporters: Sequence and structure comparison

The Saccharomyces cerevisiae genome contains three genes encoding alkali metal cation/H+ antiporters (Nha1p, Nhx1p, Kha1p) that differ in cell localization, substrate specificity and physiological function. Systematic genome sequencing of other yeast species revealed highly conserved homologous ORFs in all of them. We compared the yeast sequences both at DNA and protein levels. The subfamily of yeast endosomal/prevacuolar Nhx1 antiporters is closely related to mammalian plasma membrane NHE proteins and to both plasma membrane and vacuolar plant antiporters. The high sequence conservation within this subfamily of yeast antiporters suggests that Nhx1p is of great importance in cell physiology. Yeast Kha1 proteins probably belong to the same subfamily as bacterial antiporters, whereas Nhal proteins form a distinct subfamily.