Muscle amino acid composition

The fifth was a molecular biologist, who smiled sweetly and pointed out that all the others had missed the point. The frog jumps because of the biochemical properties of its muscles. The muscles are largely composed of two interdigitated filamentous proteins, actin and myosin, and they contract because the protein filaments slide past each other. This property of the actin and myosin is dependent on the amino acid composition of the two proteins, and hence on chemical, and thus on physical properties. In the last analysis, the molecular biologist insisted, following James Watson, we are all nothing but subatomic particles. 

Discarded fish bones and cutoffs may contain considerable amounts of muscle proteins. These muscle proteins are nutritionally valuable and easily digestible with well-balanced amino acid composition (Venugopal et al., 1996). Therefore, fish proteins derived from seafood processing by-products can be hydrolyzed enzymatically to recover protein. Protein hydrolysates from several marine species have been analyzed for their nutritional and functional properties, and researches have mainly explored the possibility of obtaining biologically active peptides (Benkajul and Morrissey, 1997). Moreover, skipjack tuna muscle (Kohama et al., 1988), sardine muscle (Bougatef et al., 2008), and shark meat (Wu et al., 2008) have been used to separate potential peptides. 

Additional information <1, 2, 5, 7, 25> (<1,2,5,25> molecular weights of enzymes from different organisms [34] <1,2,5> comparison of amino acid composition of different sources [5,17] <1,2,5> a great deal of homology and some distinct differences between liver and muscle type enzymes of different organisms [5] <7> amino acid composition [40]) [5, 17, 34, 40]... 

The enzyme, which has been isolated from many species, is a tetramer of Mr 140 000. The two forms of the enzyme, the H4, predominating in heart muscle, and the M4, predominating in skeletal muscle, give rise to a family of isozymes.46,47 The amino acid composition of the polypeptide chain that constitutes the M4 form is significantly different from that of the H4 form, and the two have different kinetic properties. Despite this, the sites for the association of the subunits had to... 

The molecular weight of muscle FDPase, based on sucrose density gradient experiments, was estimated to be 133,000, similar to that of liver FDPase (64)- However, the muscle enzyme did not react with antibody prepared against purified rabbit liver FDPase (63), and its amino acid composition differed significantly (74). In particular, the muscle enzyme contained fewer histidine and methionine residues but was richer in tyrosine and arginine. Tryptophan is absent in all of the mammalian FDPases thus far examined, with the possible exception of FDPase from swine kidney (65). The muscle and liver enzymes could also be distinguished on the basis of their electrophoretic mobility (74) ... 

At least two distinct FDPases are found in animal tissues, one in liver and kidney, and the other in white muscle. The liver and kidney enzymes show minor differences in amino acid composition and in their response to agents, such as pyridoxal phosphate (4%), but these differences may be the result of modification during isolation (see above). On the other hand, the muscle enzyme is distinctly different in immunological properties as well as in amino acid composition (63, 74). All of the mammalian FDPases are similar in having a molecular weight of approximately 135,000, and all are composed of four subunits the... 

The exact form in which non-crosslinked elastin is secreted from smooth muscle cells is yet to be clearly defined. Foster et al. (36) have suggested that a non-cross linked elastin (pro-elastin) is secreted from smooth muscle cells in a form that is approximately 120,000 to 140,000 daltons. They have suggested that proelastin is cleaved to smaller molecular weight forms of non-crosslinked elastin. It should be noted, however, that this view is not entirely supported by data from other laboratories. There are two reports on the use of isolated mRNA from chick aorta suggesting only a 70,000 dalton non-cross linked elastin is the major product of translation (37,38). There is also a recent report suggesting that aortic mRMA translates a 200,000 dalton putative elastin product (39). We have recently isolated a non-crosslinked elastin from the aortas of copper deficient chicks that appears to be 100,000 daltons (27). Its amino acid composition is similar to that for tropoelastin (Table III). A major problem in resolving these points is that the trypsin-like proteinase associated with elastin is not easily denatured or separated from the non-crosslinked forms of elastin. The proteinase is also not readily inhibited by commonly used inhibitors for trypsin-like proteinases (26). 

Myosin. Rabbit muscle myosin is a long, thin molecule (VI400 X 20-50 A) with a molecular weight of 5 X 10. It is composed of two heavy chains and four light chains as demonstrated by SDS-polyacrylamide disc gel electrophoresis. On tryptic digestion, myosin is split into the subunits, H-meromyosin (HMM) and L-mero-myosin (LMM). HMM is further split into S-l and S-2 subunits. While LMM is a rod of V)0% a-helical content, the a-helical content for HMM, S-l and S-2 fragments is 46%, 33% and 87%, respectively. The ATPase activity is localized in the S-l subunit (33,34). Although fish myosins appear to have the same structural profile (10,22,35-40) and similar amino acid composition as rabbit myosin (39,41,42), fish myosin is different from rabbit myosin in physicochemical properties such as solubility, viscosity and stability (10,22,35-40). 

Actin. Rabbit muscle G-actin is globular with a molecular weight of 4.2 X 104. In the presence of salts it is polymerized into F-action (34). The principal properties of fish actin (35-37,40, 43,44), including amino acid composition (41), are similar to rabbit actin, but fish actin is more readily extracted from wet muscle by salt solutions as a viscous solution of actomyosin (22,35,36,45). 

The amino acid compositions of two phosphorylases have been determined, and are shown in Table XVI. The complete, amino acid sequence or three-dimensional structure of a phosphorylase is not yet known, and the task of delineating it will be difficult because of the large size of the molecules. However, the sequence of amino acids about an important phosphoserine residue has been reported for rabbit and human muscle phosphorylase a. In the rabbit enzyme, the sequence is... 

Amino Acid Composition" of Phosphorylase b of Babbit Muscle and Human Muscle... 

Neurokinin A and B are both decapeptides discovered by Kimura et al. (142) from the porcine spinal cord. Both have very similar amino acid composition and sequence homology to the undecapeptide substance P, and they also have similar biological activities as substance P. They are potent bronchoconstrictors, constrict smooth muscle, and activate the micturition reflex. 

It is probable that Bailey s first interest in the muscle field, in which lies his greatest contribution, was aroused by the work of Astbury and Dickinson who showed that fibers of denatured myosin behaved in ways similar to keratin so far as their elastic properties were concerned and their structures were revealed by X-ray analysis. At this time the Chibnall group was much interested in the amino acid composition of proteins. The obvious similarities in fibrous behavior between keratin and myosin despite their differences in amino acid composition, particularly in cystine content, stimulated Bailey to make a comparative study of the composition of some of the then recognized muscle proteins. This was Bailey s first paper on muscle and extension of the... 

The typical acute phase response included increases in C-reactive protein, fibrinogen. .. amounting to a total increased in acute phase protein of 850 mg/kg body weight. To cover the requirements for all amino acids to support this increased synthesis of hepatic proteins, a breakdown of1980 mg/kg of muscle proteins were required, because there is a mismatch between the amino acid composition of the APP and muscle proteins . 

Ohashi and Maruyama (1979) isolated a 55-kDa protein from chicken breast muscle that formed a lattice structure with a periodicity of 8 nm. This protein, termed Z protein, is the only known candidate for the lattice structure of Z lines. Although the molecular weight of Z protein is similar to that of desmin, the amino acid compositions are entirely different. The Z protein is located in the interior of Z lines as revealed by an immunofluorescent technique (Ohashi et al., 1982). 

Study of the molecular biology of calcium regulation of muscle contraction was initiated by the discovery of a new protein factor sensitizing actomyosin to calcium ions (Ebashi, 1963 Ebashi and Ebashi, 1964). This protein factor was called native tropomyosin, because of its similarity in amino acid composition to tropomyosin, which had been discovered earlier (Bailey, 1946, 1948). It was soon found that this factor is a complex of tropomyosin and a new globular protein, termed troponin (Ebashi and Kodama, 1965 Ebashi et al., 1968). Thus four proteins, i.e., myosin, actin, troponin, and tropomyosin, are involved in calcium-regulated physiological muscle contraction (Ebashi et al., 1968, 1969 Ebashi and Endo, 1968). The contractile interaction between myosin and actin is depressed by troponin and tropomyosin in the absence of calcium ions. When calcium ion acts on troponin, this depression is removed and the contractile interaction is then activated (Figs. 1 and 2). 

D-Fructose 1,6-diphosphatases from rabbit liver and muscle are similar in their cation-requirement profile, molecular weight, substrate affinity, and substrate inhibition, but have different amino acid compositions, and the muscle enzyme does not cross-react with antibody to the purified liver-enzyme.361,364 The muscle enzyme is more sensitive to AMP than the enzyme from liver or kidney.385... 

Detailed chemical investigation of the parvalbumins began with the demonstration that the low molecular weight myogens of carp white muscle were composed of three components, designated as 2, 3 and 5, which could be separated electrophoresis (102). These proteins were not present in red muscle of cod (102), demonstrating a protein difference between the two types of muscle. The three cod parvalbumins have been crystallized (103) and their amino acid composition has been determined. The three proteins have only small differences in amino acid composition, molecular weight and other physical properties. 

Table 5. Amino acid composition of calcium-binding proteins from muscle...

Reeds, P. J., Field, C. R., and Jahoor, F. (1994). Do the differences between the amino acid compositions of acute-phase and muscle proteins have a bearing on nitrogen loss in traumatic states /. Nutr. 124, 906-910. 

III. AMINO ACID COMPOSITION OF SMOOTH MUSCLE CALCIUM BINDING PROTEINS... 

Troponin is a heterotrimeric protein involved in the regulation of striated and cardiac muscle contraction. Most troponin in the cell is bound to the actin-tropomyosin complex in the muscle fibril. The three subunits of troponin consist of troponin-C, troponin-T, and troponin-l, each with a specific function in the regulatory process. Troponin-T and troponin-l exist as different isoforms in cardiac and skeletal muscle (sequences with a different amino acid composition), thus allowing the development of specific antibodies against each form. As a consequence, either cardiac troponin-T or cardiac troponin-l may be rapidly measured in blood samples by immunoassay with a good degree of specificity. 

Amino acids that enter the blood are transported across cell membranes of the various tissues principally by Na -dependent cotransporters and, to a lesser extent, by facilitated transporters (Table 37.1). In this respect, amino acid transport differs from glucose transport, which is Na -dependent transport in the intestinal and renal epithelium but facilitated transport in other cell types. The Na dependence of amino acid transport in liver, muscle, and other tissues allows these cells to concentrate amino acids from the blood. These transport proteins have a different genetic basis, amino acid composition, and somewhat different specificity than those in the luminal membrane of intestinal epithelia. They also differ somewhat between tissues. For instance, the N system for glntamine nptake is present in the liver bnt either not present in other tissues or present as an isoform with different properties. There is also some overlap in specificity of the transport proteins, with most amino acids being transported by more than one carrier. 

Similarly, if one compares the form of the enzyme lactate dehydrogenase found in heart muscle to the type found in skeletal muscle, one can see small differences in amino acid composition. These differences in turn affect the reaction catalyzed by this enzyme, the conversion of pyruvate to lactate. The heart type has a high Kf, or a low afiinity for pyruvate, and the muscle type has a low K, or a high afiinily for pyruvate. This means that the pyruvate win be preferentially converted to lactate in the muscle but will be preferentially used for aerobic metabolism in the heart, rather than being converted to lactate. These conclusions are consistent with the known biology and metabolism of these two tissues. 

Structural proteins make up the contractile apparatus responsible for muscle movement. The amino-acid composition is roughly similar to corresponding proteins in mammalian muscle, although the... 

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