Changes In Protein Components Research Articles

Regulating the composition and secondary structure of wheat protein through canopy shading to improve dough performance and nutritional index

Viscoelastic properties of gluten proteins critically determine the biscuit-making quality. However, cultivar genetics and light conditions closely regulate the composition of the gluten proteins. The impact of pre- and post-anthesis shading (60 %) on amino acid profile, gluten protein composition, secondary structure, dough performance, and biscuit-making quality were evaluated using four wheat cultivars that differ in gluten protein composition. Pre- and post-anthesis shading increased the contents of gliadin, by 35.8 and 3.1 %; glutenin, by 27.6 and 7.3 %; and total protein, by 21.7 and 10.6 %, respectively, compared with those of unshaded plants. Conversely, the ratios of glutenin/gliadin, ω-/(α,β + γ)-gliadin, and high-molecular-weight/low-molecular-weight glutenin subunits decreased with shading. Strong-gluten cultivars exhibited smaller declines in these parameters than weak-gluten cultivars. Secondary structure analysis of the wheat protein revealed that shading increased β-sheet content but decreased β-turn content. Changes in protein components and their secondary structures caused an increase in wet gluten content, dough development time, and gluten performance index, thereby decreasing the biscuit spread ratio. Shading stress increased the protein content and nutrition index but decreased the biological value of protein by 2.5 %. Transcriptomic results revealed that shading induced 139 differentially expressed genes that decreased carbohydrate metabolism and increased amino acid metabolism, involved in increased protein content. Thus, canopy shading improves dough performance and nutrition index by regulating the amino acid profiles, protein compositions, and secondary structures. The study provides key insights for achieving superior grain quality under global dimming.

Carbonic Anhydrase III Has Potential as a Biomarker for Experimental Colitis and Functions as an Immune Regulator by Inhibiting Inflammatory Cytokine Secretion.

Simple SummaryThe mechanism underlying the onset of ulcerative colitis (UC) has not yet been elucidated in detail. Unknown components in colorectal tissue may be important risk factors to elucidate the cause of UC; however, they have not been highlighted as targets. To identify key factors, rats with dextran sulfate sodium-induced experimental colitis were used. The level of carbonic anhydrase III was significantly decreased in both the serum and colon tissues of these UC rats. Upon stimulation of peritoneal macrophages (MΦ) with lipopolysaccharide, the intracellular concentration of carbonic anhydrase III significantly decreased, while the secretion of pro-inflammatory cytokines from MΦ treated with an anti-carbonic anhydrase III antibody was negatively regulated. In conclusion, carbonic anhydrase III may be a novel regulator of experimental colitis in rats.Ulcerative colitis (UC) is characterized by chronic inflammation of the large intestine, repeated remissions, and symptom relapses. Although unknown components in colonic regions are deeply involved in the pathogenesis of UC, the causes of UC development and aggravation have not yet been elucidated in detail. To identify key factors, we investigated the changes in protein components in the large intestine of rats with dextran sulfate sodium-induced experimental colitis (UCR). The components that differed in their concentration between normal rats (WT) and UCR were carefully investigated by electrophoretic separation and mass spectrometry. Based on these results, seven proteins with different expression levels between the WT and UCR were observed. Among them, we focused on carbonic anhydrase III (CA-III) in the pathogenesis of UC. CA-III concentrations in the colon tissue and serum were quantitatively measured using an enzyme-linked immunosorbent assay (ELISA) and real-time PCR, and the levels significantly decreased in both the colon tissue and serum of UCR with the aggravation of experimental UC. In an in vitro assay, CA-III function in peritoneal macrophages (MΦ) from rats was investigated. Upon stimulation of MΦ with lipopolysaccharide (LPS), the CA-III concentration significantly decreased in the cytoplasm of these cells. MΦ treated with an anti-CAIII antibody followed by stimulation with LPS actively secreted inflammatory cytokines, particularly interleukin-6 and tumor necrosis factor-α. Therefore, CA-III in MΦ appears to be an immune regulator that suppresses the secretion of inflammatory cytokines.

Lake charr (Salvelinus namaycush) clotting response may act as a plasma biomarker of sea lamprey (Petromyzon marinus) parasitism: Implications for management and wound assessment

Sea lampreys (Petromyzon marinus) have decimated the Great Lakes fisheries over the past century, and their control is central to protecting native fish populations. Wounding data collected from host fish, including classifying wounds as Type A (penetrating the integument) or Type B (superficial), is an integral part of sea lamprey monitoring efforts and helps inform management decisions; however, wound assessment is subjective and error-prone. This study aimed to determine if protein biomarkers of parasitism could be quantified in host fish plasma to serve as a potential objective aide in current wound assessment practices. Male siscowet lake charr (Salvelinus namaycush) were parasitized in a lab setting for four days, after which the sea lamprey was removed, host blood was collected, and the wound Type recorded. A second blood sample was collected from host fish with Type A wounds 7 months later. The plasma proteome was quantified using iTRAQ, and the relative abundances of 169 proteins were compared between parasitized and non-parasitized control fish. Three functional classes of proteins were modified by sea lamprey parasitism: immune response, lipid transport, and blood coagulation. A major finding was evidence of a concerted anticoagulation response in fish with Type A wounds, including changes in protein components and regulators of fibrin clot formation, some of which did not fully recover within 7 months. A modified clotting assay yielded a smaller thrombin-induced fibrin clot from parasitized fish, supporting the proteomic results. Therefore, measuring blood clottability could improve sea lamprey damage estimates by providing a more objective and quantitative index of parasitism than is offered by wounding data alone.

Abstract 2608: MMP-7 increases migration by decreasing intercellular E-cadherin and F-actin localization in prostate cancer micro-tumors formed by perlecan/HSPG2

Abstract Introduction: Polarized epithelium is maintained by cell-cell interactions via cadherins and cell adhesion molecules (CAMs). Interactions are stabilized further by cell-matrix interactions on the basement membrane where perlecan/HSPG2 is a major component that controls signaling in resting tissues with unperturbed matrices. Proteolytic cleavage of perlecan increases cell-matrix interactions and dysregulates cell signaling, permitting migration. Previous studies showed perlecan domain IV-3 (DmIV-3) drives cell cohesion and, when digested with matrix metalloproteinase-7 (MMP-7), drives cell dyscohesion. In vivo, prostate cancer (PCa) patients with bone metastases have circulating DmIV fragments, with negative correlation between MMP-7 staining and loss of perlecan in tissue samples. MMP-7 can cleave cadherins and other CAMs disrupting cell-cell adhesions. Also, DmIV-3 fragments generated by MMP-7 cleavage may further induce cell dyscohesion by disrupting interactions between CAMs and/or cadherins. Methods: To evaluate the impact of MMP-7 and DmIV-3 fragments on cell migration or cluster dyscohesion, uniformly sized PCa cell clusters were pre-formed using a microwell system, enabling control of cluster size and cellularity. Pre-formed cell clusters were transferred to DmIV-3 coated wells for 16-24 hours. Clusters then were treated with MMP-7 alone or MMP-7 plus DmIV-3 fragments during live cell imaging and cell tracking. Immunofluorescent staining and Imaris analysis of fixed cell clusters at different stages of cohesion and dyscohesion was performed to determine cytoskeletal architecture and stability. The alignment of E-cadherin and F-actin served as a quantitative measure of cohesion. Results: PCa cell clusters maintained strong cell-cell contacts with intact DmIV-3. In contrast, pre-formed PCa cell clusters cultured in the presence of DmIV-3 cleaved by MMP-7 showed dyscohesion and increased cell migration initiated at the cluster edges where migratory velocity was highest. Pre-formed PCa cell clusters treated with MMP-7 had increased F-actin reorganization during various stages of PCa cell cluster dyscohesion. E-cadherin and F-actin co-alignment at cell-cell contacts was reduced in PCa cell clusters treated with MMP-7 and DmIV-3 fragments, particularly at the edges where cell-cell adhesion was lowest and cell-matrix interactions were highest. Conclusion: Following patterns of dyscohesion of pre-formed PCa micro-tumors provides a good model to study dynamic changes in protein components involved in cell-cell interactions and quantitate cell migration patterns as they can occur in metastasis and circulating tumor cell formation. Actin reorganization promotes a migratory cell phenotype in PCa cell clusters treated with MMP-7 and DmIV-3 fragments. Future studies aim to identify DmIV3 fragment(s) positively associated with tumor dyscohesion that may play key roles in secondary metastasis formation. Citation Format: Lissette A. Cruz, Tristen V. Tellman, Brian J. Grindel, Daniel D. Carson, Mary C. Farach-Carson. MMP-7 increases migration by decreasing intercellular E-cadherin and F-actin localization in prostate cancer micro-tumors formed by perlecan/HSPG2 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2608.

Effect of Antioxidant Preparation «Mexidol» on the Protein Components of the Erythrocyte Cytoplasmic Membrane in Patients with Ulcerative Colitis

Background . Ulcerative colitis is a colon disease accompanied by a systemic inflammatory response with the development of oxidative stress, which leads to structural and functional changes in cell membranes. There are no data on the qualitative and quantitative changes in the protein components of the cytoplasmic membrane in ulcerative colitis under the influence of the antioxidant, membrane-stabilizing drug Mexidol. The article presents the data of our own research, the purpose of which is to study the nature of changes in protein components in the erythrocyte membrane in vitro when exposed to Mexidol (the active substance is oxymethylethyl peridine succinate) in patients with ulcerative colitis during an acute attack. Materials and methods . The study involved 51 patients with ulcerative colitis during the exacerbation period and 30 clinically healthy individuals comparable by sex and age. Ten major protein components of the erythrocyte membrane were evaluated. Results . As a result of the regression analysis, it was shown that in the group of clinically healthy individuals, almost all structural proteins are to varying degrees linked to proteins by glucose transporters and the enzyme glutathione-S-transferase and in patients with ulcerative colitis, the connection of protein components of membrane channels with spectrines is lost. Incubation of red blood cells of patients with ulcerative colitis in a solution of Mexidol in vitro did not affect the protein components of the erythrocyte cytoplasmic membrane. At the same time, in ulcerative colitis patients there was a restoration of spectrin connections with anion transport proteins and a glucose transporter, which were not detected in the initial state. Conclusion . The effect of Mexidol in vitro on the erythrocyte membranes of patients with ulcerative colitis was accompanied by the restoration of structural and functional protein bonds, which can be considered as a beneficial effect of this drug on the erythrocyte membrane under the conditions of the studied pathology.

Cow's milk allergen β‐lactoglobulin immunoreactivity affected by pulsed light treatment

Cow’s milk allergy (CMA) is one of the most common food allergies especially in early childhood. One of the major allergens in cow’s milk is the beta-lactoglobulin (β-lg). High temperature processes are known to denature whey proteins causing changes in their nutritional, organoleptic or technological properties. Consequently, an important challenge is to develop non-thermal technologies which can prevent adverse thermal effects and produce safe food products. One of these non-thermal technologies, Pulsed Light (PL), is a technology that consists of a successive repetition of short duration and high power flashes of broadband emission light (200-1000 nm) that has been shown to be effective in inactivating a wide broad of microorganisms. Proteins are among the major targets for photo-induced modifications due to the abundance of endogenous chromophores within their structure. PL treatments were demonstrated to cause milk protein aggregation by disulfide bonds without further significant changes in protein components and induce conformational changes in β-lg. Despite these findings, the effect of PL on the allergenicity of proteins is still a matter of speculation. Thus, the aim of this study is to determine whether such treatment affects the immunoreactivity of the β-lg. PL treatments of β-lg from bovine milk dissolved in several media at different pH were performed in a Xenon lamp with a fluence of 4, 8, 12 and 16 J cm-2. After treatments, samples were analyzed by native-PAGE and an enzyme-linked immunosorbent assay (ELISA) with polyclonal IgG, usually used in β -lg detection kits. Results in native-PAGE showed a breakdown of the β-lg appearing some bands of lower molecular weight. The ELISA demonstrated a gradual decrease interaction allergen-IgG with the intensity of fluence applied. As results suggest, a conformational change in the protein is provoked by PL technology covering up the detection of this allergen. It will be interesting to discover whether epitopes recognized by specific IgE antibodies (responsible of triggering type I hypersensitivity responses) in the sera of patients recognize the same epitopes as those recognised by the IgG used in this study.

Changes in Protein Components and Size Distribution of Bovine Milk Fat Globules Caused by Heat Treatment

The effects of heat treatment on the changes in the protein components and size distribution of bovine milk fat globules were investigated. The results of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that some membrane proteins, such as xanthine oxidase and butyrophilin, had disappeared or were weakly stained in the gel due to heating of milk. The volume surface average diameter of raw milk fat globules ranged from 1.15 to 7.42 μm. When the heating temperature was above 90 °C or the heating time was prolonged above 10 min, the average diameters of heated milk fat globules increased significantly (P < 0.05).

A Key Claudin Extracellular Loop Domain is Critical for Epithelial Barrier Integrity

Intercellular tight junctions (TJs) regulate epithelial barrier properties. Claudins are major structural constituents of TJs and belong to a large family of tetra-spanning membrane proteins that have two predicted extracellular loops (ELs). Given that claudin-1 is widely expressed in epithelia, we further defined the role of its EL domains in determining TJ function. The effects of several claudin-1 EL mimetic peptides on epithelial barrier structure and function were examined. Incubation of model human intestinal epithelial cells with a 27-amino acid peptide corresponding to a portion of the first EL domain (Cldn-1(53-80)) reversibly interfered with epithelial barrier function by inducing the rearrangement of key TJ proteins: occludin, claudin-1, junctional adhesion molecule-A, and zonula occludens-1. Cldn-1(53-80) associated with both claudin-1 and occludin, suggesting both the direct interference with the ability of these proteins to assemble into functional TJs and their close interaction under physiological conditions. These effects were specific for Cldn-1(53-80), because peptides corresponding to other claudin-1 EL domains failed to influence TJ function. Furthermore, the oral administration of Cldn-1(53-80) to rats increased paracellular gastric permeability. Thus, the identification of a critical claudin-1 EL motif, Cldn-1(53-80), capable of regulating TJ structure and function, offers a useful adjunct to treatments that require drug delivery across an epithelial barrier.

Effect of Pulsed-Light Treatment on Milk Proteins and Lipids

Pulsed-light treatment offers the food industry a new technology for food preservation. It allows the inactivation of numerous micro-organisms including most infectious foodborne pathogens. In addition to microbial destruction, one can also question whether pulsed-light treatment induced conformational changes in food components. To investigate this question, the influence of pulsed-light treatment on protein components of milk was evaluated by using UV spectroscopy, spectrofluorometry, electrophoresis, and determination of amino acid composition. Pulsed-light treatment resulted in an increase of UV absorbance at 280 nm. The intrinsic tryptophan fluorescence of beta-lactoglobulin (BLG) showed a 7 nm red shift after 10 pulses. SDS-PAGE showed the formation of dimers after treatment of BLG by 5 pulses and more. No significant changes in the amino acid composition of proteins and lipid oxidation were observed after pulsed-light treatment. The obtained results indicated changes in the polarity of the tryptophanyl residue microenvironment of BLG solutions or changes in the tryptophan indole structure and some aggregation of studied proteins. Hence, pulsed-light treatment did not lead to very significant changes in protein components; consequently, it could be applied to process protein foods for their better preservation.

Dynamic changes in protein components of the tight junction during liver regeneration.

The construction of the hepatocyte tight junction is one of the most important events during liver regeneration leading to the reorganization of the bile canaliculi and the repolarization of hepatocytes after cell division. To understand this event at the molecular level, we examined the expression of tight junction proteins by Western blot analysis and their cellular localization by immunofluorescence microscopy in regenerating rat liver after two-thirds hepatectomy. The levels of tight junction components such as claudin-3, ZO-1 and atypical protein kinase C (PKC)-specific interacting protein (ASIP) increased two- to three-fold over control levels in coordination with a peak 2-3 days after partial hepatectomy, whereas occludin levels remained unchanged. The bile canaliculi outlined by tight junction components and actin filaments reveal significant morphological changes from 2-3 days after partial hepatectomy. During this period, claudin-3/ZO-1 and ASIP/ZO-1 were nearly co-localized, whereas occludin was locally reduced or almost absent on the bile canaliculi outlined by ZO-1 staining. The uncoupled localization of F-actin and tight junction components was often observed. The function of hepatocytes, as revealed by the serum bile acids level, was distorted temporally at an early stage of regeneration but mostly restored 3 days after partial hepatectomy. These observations suggest that the de novo construction of tight junctions proceeds mainly 2-3 days after partial hepatectomy in parallel with the cell polarization required for hepatocyte function. However, the complete normalization of the composition of the tight junction components, such as occludin and the association with F-actin, requires additional time, which may support the regeneration of fully polarized normal hepatocytes.

Long-term variations of AP-1 composition after CRH stimulation: consequence on POMC gene regulation

It has been shown previously that the CRH-induced POMC gene transcription in the corticotroph cell line AtT-20 involves an increase in AP-1 DNA binding activity that remained elevated for at least 24 h, while induction of c-fos was transient. We showed here that there were dramatic changes in protein components of AP-1 including an initial recruitment of the transcriptional activators c-Fos and Jun-B then of Fra-2 and Jun-D. Changes in AP-1 composition were concomitant with a decrease in POMC mRNA. Moreover, the presence of Fra-2/Jun-D dimers suppressed the CRH–induction of c-fos mRNA expression as well as c–Fos/Jun-B recruitment in AP-1 complexes, suggesting the existence of autoregulatory loops of AP–1 composition that involve complex interactions between the different members of the Jun and Fos families. It is concluded that CRH stimulation of corticotroph cells involves successive recruitment of activators and repressors, possibly contributing to prevent over expression of POMC.

Accumulation of secondary carotenoids in flagellates of Haematococcus pluvialis (Chlorophyta) is accompanied by an increase in per unit chlorophyll productivity of photosynthesis

Flagellates of Haematococcus pluvialis accumulate secondary carotenoids (mainly astaxanthin and its esters) under nitrogen deficiency in combination with exposure to stronger light. Our cultivation scheme allows the characterization of metabolic activities during the accumulation process without interference by formation of the resting state (aplanospores). The highest rate of secondary carotenoid biosynthesis (0.046 h−1) was observed almost simultaneously with the highest rates of cell division (0.027 h−1) and of chlorophyll biosynthesis (0.015 h−1) after 1.5 days of exposure to nitrogen limitation and higher irradiance. Photosynthetic activity was studied by oxygen evolution and chlorophyll fluorescence measurements; changes in protein components of the photosynthetic apparatus were quantified by gel electrophoresis and immunoblot analysis. Accumulation of secondary carotenoids was accompanied by an increase in photosynthetic productivity expressed on a unit chlorophyll basis. Changes in the photosynthetic apparatus occurring mainly during the first 2 days of exposure to nitrogen limitation and stronger light can be interpreted as acclimation to the increased cultivation irradiance. Photoprotective action of secondary carotenoids as a ‘sunshade’ was demonstrated in red flagellates exhibiting a lower blue-light-induced decrease in photosystem II efficiency as compared with red actinic light.

Accumulation of secondary carotenoids in flagellates of Haematococcus pluvialis (Chlorophyta) is accompanied by an increase in per unit chlorophyll productivity of photosynthesis

Flagellates of Haematococcus pluvialis accumulate secondary carotenoids (mainly astaxanthin and its esters) under nitrogen deficiency in combination with exposure to stronger light. Our cultivation scheme allows the characterization of metabolic activities during the accumulation process without interference by formation of the resting state (aplanospores). The highest rate of secondary carotenoid biosynthesis (0.046 h−1) was observed almost simultaneously with the highest rates of cell division (0.027 h−1) and of chlorophyll biosynthesis (0.015 h−1) after 1.5 days of exposure to nitrogen limitation and higher irradiance. Photosynthetic activity was studied by oxygen evolution and chlorophyll fluorescence measurements; changes in protein components of the photosynthetic apparatus were quantified by gel electrophoresis and immunoblot analysis. Accumulation of secondary carotenoids was accompanied by an increase in photosynthetic productivity expressed on a unit chlorophyll basis. Changes in the photosynthetic apparatus occurring mainly during the first 2 days of exposure to nitrogen limitation and stronger light can be interpreted as acclimation to the increased cultivation irradiance. Photoprotective action of secondary carotenoids as a ‘sunshade’ was demonstrated in red flagellates exhibiting a lower blue-light-induced decrease in photosystem II efficiency as compared with red actinic light.

Changes in protein components and storage stability of Royal Jelly under various conditions

The changes in quality of Royal Jelly (RJ) stored at −20 °C, 4 °C, and room temperatures under dark and light conditions for up to 7 months were investigated. The results showed that colour, viscosity, fractions of water-soluble protein (WSP) and simple sugars of RJ changed significantly during storage at room temperature, but not at −20 °C. The viscosity and browning intensity increased with storage time, and were enhanced by the ambient temperature. Two major fractions in WSP of RJ were obtained by gel filtration, while four to five different protein components were found when subjected to SDS-PAGE. The relative amounts and molecular weight distributions of these WSP components varied during storage. The results indicated that the quality deterioration of RJ during storage was due to the Maillard browning reaction.

Possible participation of angiotensin II receptor subtype 1 in development of hypertension

It has been shown previously that the CRH-induced POMC gene transcription in the corticotroph cell line AtT-20 involves an increase in AP-1 DNA binding activity that remained elevated for at least 24 h, while induction of c-fos was transient. We showed here that there were dramatic changes in protein components of AP-1 including an initial recruitment of the transcriptional activators c-Fos and Jun-B then of Fra-2 and Jun-D. Changes in AP-1 composition were concomitant with a decrease in POMC mRNA. Moreover, the presence of Fra-2/Jun-D dimers suppressed the CRH–induction of c-fos mRNA expression as well as c–Fos/Jun-B recruitment in AP-1 complexes, suggesting the existence of autoregulatory loops of AP–1 composition that involve complex interactions between the different members of the Jun and Fos families. It is concluded that CRH stimulation of corticotroph cells involves successive recruitment of activators and repressors, possibly contributing to prevent over expression of POMC.

Effect of serum on the isolated CNS myelin membrane

Rabbit brain myelin was incubated with rabbit serum, and changes in protein components were measured following re-isolation of the membrane by ultracentrifugation. Basic protein was substantially degraded by proteolytic enzymes present in serum. No breakdown of other major myelin proteins was observed. Some serum proteins became firmly associated with the myelin membrane during the incubation. Furthermore, the incubation of myelin with serum resulted in formation of denser myelin particles, which sedimented in 0.625 M sucrose. This process appears not to be related to the removal of basic protein from the membrane. The basic protein-digesting activity of human serum was comparable to that of rabbit serum, and no difference in the activity between sera from multiple sclerosis and control patients was observed. The possible relevance of these findings to demyelinating diseases is discussed.

The breakdown of myelin-bound proteins by intra- and extracellular proteases

Changes in protein components of purified myelin were measured following incubation in vitro with purified intra- and extracellular enzymes. Incubation with calf brain cathepsin D did not result in a significant relese of acid-soluble peptides as measured by ninhydrin analysis but was accompanied by a large loss of myelin proteins as determined on SDS-acrylamide gels. After 5 hr at 37°C there was a loss of about 25% for fast and slow basic proteins and the Agrawal proteolipid, but only a 5-10% loss for the Folch-Lees and Wolfgram components. Rat brain cathepsin D prepared by affinity chromatography gave a 30-60% breakdown of basic proteins and proteolipids. In general, breakdown using lyophilized myelin was increased over two-fold as compared to experiments with fresh myelin. Breakdown induced by cathepsin D was completely inhibited by the pentapeptide pepstatin. Incubation of myelin at physiological pH resulted in an endogenous breakdown of about 12% for basic proteins in freshly prepared, and 50% for lyophilized material. Addition of a soluble neutral proteinase that splits hemoglobin did not induce additional breakdown except for a small change in the Folch-Lees component. The extracellular enzymes pepsin and TPCK-treated trypsin resulted in a larger breakdown of all components as compared to brain enzymes. Present results demonstrate that all protein components of myelin are accessible to hydrolases and vulnerable to breakdown to varying extents by brain enzymes. These facts are consistent with the known rates for myelin protein turnover and may have a bearing on changes associated with demyelinating diseases.

EFFECT OF SMOKING PROCESS ON SOLUBILITY AND ELECTROPHORETIC BEHAVIOR OF MEAT PROTEINS

SUMMARYThe solubility characteristics and starch gel electrophoretic properties of untreated, heated, and heated and smoked pork longissimus dorsi muscle samples were investigated. The percentages of the low ionic strength fraction, the sarcoplasmic and the soluble fibrillar protein nitrogen fractions decreased in the heated and heated and smoked samples when compared to the untreated samples. The myofibrillar protein nitrogen fraction increased in the heated samples and decreased in the heated and smoked samples. The stroma fraction from the untreated to the heated state remained almost constant, but increased considerably in the heated and smoked samples. Electrophoretic studies of the sarcoplasmic fraction indicated numerous changes in the heated and heated and smoked samples. The electropherograms of the heated and smoked samples from the Weber‐Edsall and meat‐urea extracts showed definite changes in protein components. These studies indicated that smoke definitely caused changes in protein solubility and the electrophoretic behavior of meat proteins.