Myosin essential chain

S ATP -I- myosin I heavy chain <1, 2, 9-11> (<10> major site of phosphorylation is Ser8 [22] <2> 35 kDa trypsin fragment of the C-terminus of the maximally activated, phosphorylated enzyme is fully catalytically active and contains 2 thirds of the autophosphorylation sites of the native enzyme [20] <9,10> substrate myosin ID [19,22] <2> higher activity with membrane-bound substrate myosin I [17] <2> substrates are heavy chains of myosin lA and IB [6,7,17] <2,11> substrate is heavy chain of myosin IC [7,23,24] <2> a basic amino acid is essential on amino-terminal side of phosphorylation site, two are preferable, and a Tyr-residue is essential two residues away on the COOH-terminal side [7] <2> contains two myosin heavy chain kinases one for myosin I and one for myosin II... 

Timson, D.J., Trayer, H. R., and Trayer, I. P. (1998). The N-terminus of Al-type myosin essential light chains binds actin and modulates myosin motor function. Eur. 

Moretti A, Weig HJ, Ott T, Seyfarth M, HolthoffHP, Grewe D, et al. Essential myosin light chain as a target for caspase-3 in failing myocardium. Proc Natl Acad Sci USA 2002 99 11860-11865. 

Figure 34.5. Myosin Light Chains. The structures of the essential and regulatory light chains from muscle myosin are compared with the structure of calmodulin. Each of these homologous proteins binds an a helix (not shown) by wrapping around it.

Chapter 1, this volume). Phosphorylation is also essential for movement of actin filaments in both the Nitella and the sliding actin in vitro motility assays (Umemoto and Sellers, 1990 Warshaw etai, 1990 Sellers etal., 1985). The site of the regulatory phosphorylation is Ser-19 on the LC20 (Pearson et al., 1984). Myosin light chain kinase (MLCK) also phosphorylates Thr-18, albeit at a much lower rate (Ikebe et al., 1986). Thr-18 phosphorylation increases the actin-activated MgATPase activity (Ikebe et al., 1988), but does not increase the rate of actin filament sliding in either of the two motility assays (Sellers et al., 1985 Okagaki et al, 1991). 

Babij P, Periasamy M (1989) Myosin heavy chain isoform diversity in smooth muscle is produced by differential RNA processing. J Mol Biol 210 673-679 Bagchi IC, Huang Q, Means AR (1992) Identification of amino acids essential for calmodulin binding and activation of smooth muscle myosin light chain kinase. J Biol Chem 267 3024-3029... 

The multiple non-muscle-type myosin heavy chain isoforms can be grouped into two myosin heavy chain A and B types, the latter being predominantly expressed in brain (Sun and Chantler 1992, Takahashi et al. 1992) and the former essentially in muscle and in non-muscle-non-brain tissues (Murakami et al. 1993). 

Figure 9.30 Flow diagram of the energy chain from food to essential processes in human life. The ATP utilised by the NayK ATPase maintains the ion distribution in nerves that is essential for electrical activity and, in addition, maintains neurotransmitter synthesis, both of which provide communication in the brain and hence consciousness, learning and behaviour (Chapter 14). ATP utilisation by myosin ATPase is essential for movement and physical activity. ATP utilisation by the flagellum of sperm is essential for reproduction and ATP utilisation for synthesis of macromolecules is essential for growth.

The work that follows pertains primarily to actin networks. Many proteins within a cell are known to associate with actin. Among these are molecules which can initiate or terminate polymerization, intercalate with and cut chains, crosslink or bundle filaments, or induce network contraction (i.e., myosin) (A,11,12). The central concern of this paper is an exploration of the way that such molecular species interact to form complex networks. Ultimately we wish to elucidate the biophysical linkages between molecular properties and cellular function (like locomotion and shape differentiation) in which cytoskeletal structures are essential attributes. Here, however, we examine the iri vitro formation of cytoplasmic gels, with an emphasis on delineating quantitative assays for network constituents. Specific attention is given to gel volume assays, determinations of gelation times, and elasticity measurements. 

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