Polyacrylamide gel electrophoretic methods in the separation of structural muscle proteins

Muscle fiber type and metabolic profiles of four muscles from the African black ostrich

Muscle fiber type, fiber cross-sectional area (CSA), enzyme activities (citrate synthase (CS), 3-hydroxyacetyl Co A dehydrogenase (3HAD), lactate dehydrogenase (LDH) and phosphofructokinase (PFK)) and glycogen content were analyzed in the M. iliotibialis cranialis (ITC), M. iliotibialis lateralis, M. gastrocnemius (G) and M. fibularis longus (FL) muscles from 24 ostriches. Type I and II fiber proportions were similar across the 4 muscles, but the ITC had overall the smallest fibers. CS activity was the highest in the ITC, but similar between the remainder of the muscles. 3HAD activities were very low in all muscles, ranging between 1.9 and 2.7 μmol/min/g protein, indicating poor β-oxidation. The ITC also had the lowest PFK activity. Glycogen content averaged ∼85 mmol/kg dry weight across the muscles with large intramuscular variations. The 4 ostrich muscles present with low fat oxidation capacity and low glycogen content, which could have significant implications on meat quality attributes.

Roça R, Bezerra LR, Francisco CL, Oliveira RL. Differences between cattle and buffalo in the water-soluble proteins of the Longissimus muscle as shown by electrophoretic techniques

Context Fraudulent information about food is an old and widespread problem, particularly regarding products with high economic value, such as meat and meat products. The motivation for food fraud is economic, but it can have serious impacts on public health, thus creating a food security problem. Approximately 90% of buffalo meat is marketed as beef in various regions where the consumption of buffalo meat is considered unusual. Aims To determine the electrophoretic profile of the raw Longissimus dorsi of cattle and buffalo species and to test the hypothesis that electrophoresis techniques can be used to distinguish meat from cattle from buffalo meat. Methods Fourteen 10-g samples of Longissimus dorsi (12th and 13th rib) tissue were taken from each animal of both species after slaughter. The meat of each species was analysed by native polyacrylamide gel electrophoresis (NATIVE PAGE) and by denaturing and non-denaturing sodium dodecyl sulfate (SDS)–PAGE. Differences (P < 0.05) were observed between water-soluble cattle and buffalo muscle proteins in both NATIVE PAGE (relative mobilities and percentages of protein bands) and non-denaturing and denaturing SDS–PAGE (molecular weights in kDa and optical density index). Key results With the NATIVE PAGE technique, 10 protein bands were observed in the gel, and three of these bands exhibited differences between species (P ≤ 0.05). The non-denaturing and denaturing SDS–PAGE techniques yielded significantly different protein bands in the gel. The electrophoretic profiles of some cattle and buffalo muscle proteins are distinct; therefore, raw meat flesh samples of these animal species can be distinguished using these electrophoresis techniques. Conclusions Each of the three electrophoresis techniques used can distinguish meat from different animal species; however, when there is doubt about the animal species, the use of more than one electrophoretic technique is recommended, so as to obtain more reliable results. Implications The use of electrophoresis techniques to differentiate cattle and buffalo meat is promising. This technique could be used in cases of suspected food fraud, such as the replacement of beef with buffalo or vice versa, with reliable results that will be accepted by supervisory bodies.

Comparative Skeletal Muscle Proteomics Using Two-Dimensional Gel Electrophoresis

The pioneering work by Patrick H. O’Farrell established two-dimensional gel electrophoresis as one of the most important high-resolution protein separation techniques of modern biochemistry (Journal of Biological Chemistry1975, 250, 4007–4021). The application of two-dimensional gel electrophoresis has played a key role in the systematic identification and detailed characterization of the protein constituents of skeletal muscles. Protein changes during myogenesis, muscle maturation, fibre type specification, physiological muscle adaptations and natural muscle aging were studied in depth by the original O’Farrell method or slightly modified gel electrophoretic techniques. Over the last 40 years, the combined usage of isoelectric focusing in the first dimension and sodium dodecyl sulfate polyacrylamide slab gel electrophoresis in the second dimension has been successfully employed in several hundred published studies on gel-based skeletal muscle biochemistry. This review focuses on normal and physiologically challenged skeletal muscle tissues and outlines key findings from mass spectrometry-based muscle proteomics, which was instrumental in the identification of several thousand individual protein isoforms following gel electrophoretic separation. These muscle-associated protein species belong to the diverse group of regulatory and contractile proteins of the acto-myosin apparatus that forms the sarcomere, cytoskeletal proteins, metabolic enzymes and transporters, signaling proteins, ion-handling proteins, molecular chaperones and extracellular matrix proteins.

Kate Bárány: a life of science, teaching, and service

We celebrate the lives of Michael and Kate Bárány in this issue of the Journal of Muscle Research and Cell Motility. Kate and Michael died within weeks of each other in 2011. Joe Chalovich has written about Michael and we write about Kate. As emphasized by Joe, Kate, and Michael were remarkable individuals who survived the Holocaust, the Hungarian revolution, and emerged from as much adversity as one might imagine to become productive scientists, educators, citizens, and symbols of the durability of the human spirit. They present their own story in an essay (Bárány and Bárány 2000) published in a monograph "Selected Topics in the History of Biochemistry." Rather than repeating much of the list of scientific achievements chronicled in these papers, we focus here on Kate, especially in her role as an individual and partner in science, while at the same time being an accomplished teacher, and a champion of women in science.

Detection of myofibrillar proteins using a step gradient minigel with an ambiguous interface

Myosin heavy chain (MHC), actin, titin, and nebulin are four major myofibrillar proteins that interact with each other. However, it is difficult to analyze the four proteins simultaneously on the same minigel due to their broad range of molecular weights. Numerous gradient gels are normally used to detect these myofibrillar proteins. The conventional step gradient gel provides better separation of the four major proteins, but several proteins accumulate at the interfaces between different gradient layers. To eliminate the obvious interfaces, we employed a plastic syringe filled with 12 and 4% acrylamide solutions simultaneously and then established an improved step gradient minigel with an ambiguous interface. It was determined by blue dextran in-gel visualization and scanning densitometry that the acrylamide concentration at the ambiguous interface gradually changed. Coomassie blue staining and immunoblotting revealed that the four proteins were successfully separated and transferred for analysis. This gel system is simple to prepare and easy to use, and it is a reliable method for analyzing myofibrillar proteins or other protein mixtures with broad molecular masses.

Preparative reversed-phase liquid chromatography of proteins from rabbit skeletal troponin, a multi-protein complex

A reversed-phase high-performance liquid chromatography protocol for purification of all proteins in a multi-protein (TnI, TnC, TnT, tropomyosin) complex from rabbit skeletal muscle has been developed, enabling efficient purification of sample amounts ranging from 43 mg of protein complex on a standard analytical column, to 1400 mg on a column of 21.2 mm I.D. and finally, to 5700 mg on a column of 50 mm I.D. Due to problems associated with scale-up procedures for these proteins (e.g. aggregation and/or solubility issues), an initial sample fractionation was devised whereby 50% of the TnC component was precipitated with acetonitrile prior to sample introduction on the RPLC column. By subsequently taking advantage of sample overload conditions to enhance the displacement effect between sample components, coupled with very slow gradient conditions (0.1% acetonitrile/min), we were able to achieve excellent protein separations at high yields of purified proteins.

Cardiac protein phosphorylation: functional and pathophysiological correlates

Protein phosphorylation acts a pivotal mechanism in regulating the contractile state of the heart by modulating particular levels of autonomic control on cardiac force/length relationships. Early studies of changes in cardiac protein phosphorylation focused on key components of the excitation-coupling process, namely phospholamban of the sarcoplasmic reticulum and myofibrillar troponin I. In more recent years the emphasis has shifted towards the identification of other phosphoproteins, and more importantly, the delineation of the mechanistic and signaling pathways regulating the various known phosphoproteins. In addition to cAMP- and Ca(2+)-calmodulin-dependent kinase processes, these have included regulation by protein kinase C and the ever-emerging family of growth factor-related kinases such as the tyrosine-, mitogen- and stress-activated protein kinases. Similarly, the role of protein dephosphorylation by protein phosphatases has been recognized as integral in modulating normal cardiac cellular function. Recent studies involving a variety of cardiovascular pathologies have demonstrated that changes in the phosphorylation states of key cardiac regulatory proteins may underlie cardiac dysfunction in disease states. The emphasis of this comprehensive review will be on discussing the role of cardiac phosphoproteins in regulating myocardial function and pathophysiology based not only on in vitro data, but more importantly, from ex vivo experiments with corroborative physiological and biochemical evidence.