Worm Breeder's Gazette 1(2): 22
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We have been working on the purification of native myofilament proteins from wild-type C. elegans and have determined some of their biochemical and structural properties. Procedures have been developed for isolating myosin, paramyosin, actin and tropomyosin at greater than 90% purity, from the same batch of worms. Nematode myosin. Our purified myosin is, presumably, a mixture of all nematode classes of myosin. The properties described below therefore represent average properties of all myosins. We are currently comparing the myosins of N2 with E190 and E675. In E190, the concentration of unc 54 myosin seems insignificant, while E675 contains an altered unc 54 product. Properties: 1) Besides the 210,000 heavy chains, it contains 2 light chain classes: 18,000 and 16,000 daltons. Both classes are present in E190 and E675. 2) The Ca2+-ATPase (10mM CaCl2) is comparable with rabbit skeletal muscle myosin. 3) The Mg2+-ATPase (2mM MgCl2 - 0.2mM CaCl2) is stimulated up to twofold by rabbit actin. This activity is very labile. 4) The myosin forms either very long filaments with no apparent polarity, or short, very compact bipolar structures, when ionic strength is lowered to 0.1M in 10mM MgCl2. The type of aggregate depends on whether the sample is precipitated slowly by dialysis, or rapidly by dilution. Dialysis of nematode myosin and paramyosin together yields filaments with a paramyosin core and a surface coating of myosin. Nematode tropomyosin. This is unusual in having a higher molecular weight (40,000 by SDS gel electrophoresis) than has been reported for any other tropomyosin. It forms paracrystals with a 38.0-39.0nm repeat, but a different molecular packing to rabbit skeletal muscle tropomyosin. Calcium regulation of contraction in C. elegans. Activation of the ATPase of purified nematode myosin by rabbit actin is Ca2+-requiring. Similarly, activation of rabbit heavy meromyosin (calcium independent) by crude nematode thin filaments is stimulated 3-fold by Ca2+. Nematode muscle apparently contains both thick and thin filament linked calcium regulatory systems.