Skeletal muscle troponin

Magnesium is also of interest as a replacement for Ca(ll) in calcium-requiring enzymes. In some of these, the replacement is simple (Lewinski and Lebioda, 1986), and in others it cannot occur. NMR studies show that magnesium can bind in the calcium sites of troponin C (Tsuda et al., 1990). The structure of turkey skeletal muscle troponin C has recently been reported (Herzberg and James, 1985). In one domain the replacement of Ca(II) by Mg(II) causes a conformational change, but in the other domain it does not. 

Tsuda, S., Ogura, K., Hasegawa, Y., Vagi, K., and Hikichi, K. (1990). H NMR study of rabbit skeletal muscle troponin C Mgf -Induced conformational change. Biochemistry 29, 4951-4958. 

Collins, J. H., Potter, J. D., Horn, M. J., Wilshire, G., and Jackman, N. Structural studies on rabbit skeletal muscle troponin C Evidence for gene replication and homology with calcium binding proteins from carp and hake muscle. In calcium binding proteins (eds. 

Pearlstone, J. R., and Smillie, L. B. (1985). The interaction of rabbit skeletal muscle troponin-T fragments with troponin-I. Can.]. Biochem. Cell. Biol. 63, 212-218. 

Slupsky, C. M., and Sykes, B. D. (1995). NMR solution structure of calcium-saturated skeletal muscle troponin C. Biochemistry 34, 15953-15964. 

A protein with a similar dumbell shape and structure is troponin C of skeletal muscles. Troponin C binds to a complex of proteins that assemble on the thin actin filaments of muscle fibers and control con-trachon in response to changes in the calcium ion con-centrahon (Chapter 19). Other proteins that contain EF-hand mohfs and are therefore responsive to Ca + include spectrin of cell membranes, clathrin light chains from coated vesicles, the extracellular osteonectin of bones and teeth, ° and a birch pollen anhgen. 2 Another group of 17 or more small SlOO EF-hand proteins play a variety of other roles. One of these, which has a high affinity for Zn +, has been named psoriasin because of its 5-fold or greater... 

Troponin C is the Ca +-binding subunit of troponin, and it is structurally highly homologous to calmodulin. Skeletal-muscle troponin C (sTnC 18... 

A ribbon backbone representation of the three-dimensional structure of turkey-skeletal-muscle troponin C according to Herzberg and James. The crystals were grown at pH 5 in the presence of excess Ca , and at this low pH only Ca ions bound to the high-affinity domain (the C-terminal domain) are observed. Note the high stmctural homology with calmodulin (Figure 3.17). 

Domain 3 stretches from amino acids 463 (432) to 645 (589) and corresponds to exons 5, 6, and 7. The core of domain 3 is again a single a-helix stabilized by intrahelix salt bridges. The sequence from 565 (509) to 621 (565) is 43% identical to the amino acids 90-146 of rabbit skeletal muscle troponin T, which is a TM binding site in troponin T. Domain 4 stretches from 646 (590) to the C terminus and corresponds to exons 8-13. This is an extended and stably folded region that contains little regular secondary structure (Levine et al.,... 

The finding that CP is phosphorylated in vitro but not in the intact muscle is reminiscent of that of the inhibitory component of skeletal muscle troponin, which can be phosphorylated (Stull et al., 1972) and dephosphorylated (England et al., 1972) in vitro but is not phosphorylated during contraction of intact skeletal muscle (Barany et al., 1974). Apparently, protein residues that are free for phosphorylation in vitro may participate in bond formation or are buried in situ and. 

Smillie, LB., Gologinska, K. Reinach, F.C. (1988). Sequences of complete cDNAs encoding four variants of chicken skeletal muscle troponin T. ]. Biol. Chem., 263, 18816-20. 

Tonomura, Y, S. Matsushima, E. Kashiwagi, K. Fujisawa, S. Takagi, Y. Nishimura, R. Fukushima, M. Torii, and M. Matsubara (2012). Biomarker panel of cardiac and skeletal muscle troponins, fatty acid binding protein 3 and myosin light chain 3 for the accurate diagnosis of cardiotoxicity and musculoskeletal toxicity in rats. Toxicology 302(2-3) 179-189. 

Major progress continues to be reported in a number of extremely important areas. Among the muscle proteins, the complete sequence of rabbit skeletal muscle troponin T (259 residues) has been reported.The two forms of this protein from chicken breast and leg muscle differ in their A-terminal regions, the breast muscle enzyme carrying an extra 24 residues, rich in L-histidine and l-alanine. " Troponin I from a number of different sources has been studied. " Further structural studies on myosin light chains and actins from different sources have been reported. 

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