Myosin amino acid sequence

McLachlan, A., 1984. Structural implications of die myosin amino acid sequence. Annual Review of Biophysics and Bioengineering 13 167—189. 

Fibrous proteins are long-chain polymers that are used as structural materials. Most contain specific repetitive amino acid sequences and fall into one of three groups coiled-coil a helices as in keratin and myosin triple helices as in collagen and p sheets as in silk and amyloid fibrils. 

Approximately 500 of the 820 amino acid residues of the myosin head are highly conserved between various species. One conserved region, located approximately at residues 170 to 214, constitutes part of the ATP-binding site. Whereas many ATP-binding proteins and enzymes employ a /3-sheet-a-helix-/3-sheet motif, this region of myosin forms a related a-f3-a structure, beginning with an Arg at (approximately) residue 192. The /3-sheet in this region of all myosins includes the amino acid sequence... 

Figure 1. An unrooted phylogenetic tree of the myosins based on the amino acid sequence comparison of their head domains demonstrating the division of the myosin superfamily into nine classes. The lengths of the branches are proportional to the percent of amino acid sequence divergence and a calibration bar for 5% sequence divergence is shovk n. The different classes of myosins have been numbered using Roman numerals in rough order of their discovery and hypothetical models of the different myosin structures are shown. Question marks indicate either hypothetical or unknown structural features, and only a fraction of the known myosins are shown. (Taken, in modified form, from Cheney et al., 1993).

Myosins II from other sources have similar structures. For example, analysis of the DNA sequence for a heavy chain gene from the nematode Caenorhabditis showed that the protein contains 1966 residues, 1095 of which contain an amino acid sequence appropriate for a 160-nm long coiled coil.123 There are no prolines within this sequence, which lies between Pro 850 and... 

Collins, J. H. Homology of myosin light chains, troponin-C and parvalbumins deduced from comparison of their amino acid sequences. Biochem. Biophysic. Res. Comm. 58, 301-308 (1974). 

J Frank, G., and Weeds, A. G. The amino-acid sequence of the alkali light chains of rabbit skeletal-muscle myosin. Eur. J. Biochem. 44, 317-334 (1974). 

Cohen, C., Lanar, D. E., and Parry, D. A. D. (1987). Amino acid sequence and structural repeats in schistosome paramyosin match those of myosin. Biosci. Rep. 7, 11-16. 

McLachlan, A. D., and Karn, J. (1983). Periodic features in the amino acid sequence of nematode myosin rod. / Mol. Biol. 164, 605-626. 

Parry, D. A. D. (1981). Structure of rabbit skeletal myosin Analysis of the amino acid sequences of two fragments from the rod region./. Mol. Biol. 153, 459-464. 

Comparison of the amino acid sequences of myosins, kinesins, and dyneins did not reveal significant relationships between these protein families but, after their three-dimensional structures were determined, members of the myosin and kinesin families were found to have remarkable similarities. In particular, both myosin and kinesin contain P-loop NTPase cores homologous to those found in G proteins. Sequence analysis of the dynein heavy chain reveals it to be a member of the AAA subfamily of P-loop NTPases that we encountered previously in the context of the 19S proteasome (Section 23.2.21. Dynein has six sequences encoding such P-loop NTPase domains arrayed along its length. Thus, we can draw on our knowledge of G proteins and other P-loop NTPases as we analyze the mechanisms of action of these motor proteins. 

Myosin V. An abundant myosin-family member, myosin V is isolated from brain tissue. This myosin has a number of unusual properties. First, on the basis of its amino acid sequence, each heavy chain has six tandem binding sites for calmodulin-like light chains. Second, it forms dimers but not higher-order oligomers. Finally, unlike almost all other myosin-family members, myosin V is highly processive. 

The discussion above stresses the importance of the CN4 region (residues 96-116) of troponin I in the inhibition of contractile interaction of myosin-actin in the presence of tropomyosin. The amino acid sequence of the CN4 region is shown in Fig. 3. Talbot and Hodges (1981) synthesized 12 peptide analogs of the CN4 sequence and examined their inhibitory action on actomyosin ATPase activity. The absence of residues 115 and 116 did not affect the activity, whereas the absence of residue 114 significantly decreased the inhibitory action. As to the N-terminal portion of the peptide, residues 96-103 were not essential, but the absence of Lys-105 decreased the inhibitory activity. A peptide containing the region of residues Lys-105-Val-l 14 showed about half of the inhibitory action of troponin I. The authors concluded that Lys-105 and the bulky side chain at Val-114 are essential for the inhibitory action of troponin I (Fig. 3). 

Filament assembly depends on characteristics of the myosin tail, especially the LMM, in which much of the amino acid sequence exhibits a heptapeptide repeat. If the repeat is represented as ABCDEFG, residues A and D are hydrophobic and lie at points where the a-helices... 

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