Interaction of C-Protein with Myosin1

Abstract

The effect of C-protein on the assembly reaction of myosin was studied by flow birefringence, electron microscopy, and ultracentrifugation. Myosin filaments were formed by dilution to a lower ionic strength. Thinner filaments of 70-110 A in diameter were formed in the presence of C-protein. When dilution was effected by moderately slow dilution (dilution time of 0.5-2 min) or by stepwise dilution, C-protein favored the formation of longer filaments. When dilution was effected by even slower dilution (dilution time above 2 min), C-protein favored the formation of shorter filaments. Longer filaments formed by slow dilution incorporated more C-protein than shorter ones formed by faster dilution. Addition of C-protein to a solution of myosin filaments caused association of the filaments into longer filaments. The elongation effect was slower and stronger for longer filaments.

Interaction of C-protein with pH 8.0 synthetic thick filaments prepared from the myosin of vertebrate skeletal muscle

“…C-protein appears to bind to high affinity sites on long synthetic filaments beyond the 7-8 band limit found for native filaments (0.5-0.534~m out from the centre of the bare zone) (Sj6str6m & Squire, 1977). Similar results have been obtained in some cases with pH 7.0 filaments (Miyahara & Noda, 1980). It therefore seems likely that the number of potential C-protein binding sites axially disposed along the native thick filament are governed by factors that limit filament length in vivo.…”

“…Length changes brought about by C-protein have featured prominently in these studies, but have proved difficult to interpret in mechanistic terms. Moos et al (1975) reported no consistent change in length on copolymerization, while Miyahara & Noda (1980), depending on the experimental conditions used, observed the formation of both longer and shorter filaments. Responses seen, depend to a large degree, on the rate of solvent dilution (from high to.…”

“…The normal side-by-side packing of the pH 7.0 class is disturbed at high mole ratios (Moos et al, 1975) and at low mole ratios of copolymerizing protein to myosin (Koretz, 1979). It has also been shown that long rather than short filaments appear to have a higher affinity for C-protein; this was interpreted in terms of C-protein having a lower affinity for the filament ends and bare-zone regions compared to the remainder of the structure (Miyahara & Noda, 1980).…”

The aggregation characteristics of column-purified rabbit skeletal myosin in the presence and absence of C-protein at pH 7.0

“…As with myosin alone, filament lengths are maintained over 8 d time and exhibit a normal distribution, but tend to be somewhat more peaked. In dilution experiments, no alteration of average filament length with time is observed; length distributions are hypersharp (kurtosis coefficient >>3) and maintained whether time of formation is 0 s or 7 m. Our results diverge significantly from those of Miyahara and Noda (1980), who generally used different C-protein-myosin ratios and buffers.…”

Effects of altering titin expression on myofibril assembly in a skeletal muscle cell line

“…The titin-binding site on MyBP-C has been identified within the C-terminal region, which is deleted in patients suffering fi'om the chromosome-11-associated form of familial hypertrophic cardiomyopathy, indicating the importance of the interaction between titin and MyBP-C. Furthermore, MyBP-C binds very strongly to myosin and alters myosin filament structure in vitro Koretz, 1979;Miyahara and Noda, 1980;Koretz et al, 1982;Davis, 1988). It has been proposed that MyBP-C is essential for correct thick filament formation (Gilbert et al, 1996).…”