Worm Breeder's Gazette 2(2): 25

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.

Biochemical and Genetic Studies of Contractile Proteins from Normal and Mutant Nematode Strains

H.F. Epstein, R.L Garcea, H.E. Harris, F.H. Schachat, J.A.W. LaPointe, J.M. Zengel

Myosin, actin, paramyosin and tropomyosin can be purified from N2 
and mutant strains and shown to possess native properties by different 
functional and structural tests in vitro.  One interesting 
physiological fact obtained from this approach is that, in nematode 
muscle, Ca++-mediated regulation of contraction is associated with 
proteins on both the thick and thin filaments.
The application of these methods to obtaining purified native myosin 
from various unc-54 strains has permitted us to clarify several 
questions concerning the previous observation of two kinds of myosin 
heavy chains in the body-wall.  The two kinds of myosin heavy chain 
form primarily, if not exclusively, myosin molecules containing two 
such polypeptides of either one or the other class.  The unc-54 
affected class of myosin is not required for the formation of bipolar 
or very long filaments or for complexing with paramyosin cores.  
Altered unc-54 myosin although presumably disrupting the myofilament 
lattice in vivo, is capable of normal filament assembly in vitro.  
Preliminary studies suggest that unc-54 myosin accumulates at a 
different rate than during development than the other myosins.
The two major myosins are antigenically distinct from one another.  
This fact is permitting us to purify antibodies to unc-54 myosin and 
to localize this myosin in bodywalls during development.
A tentative inference from our studies and those of others is that 
the formation of a myofilament lattice involves the interaction of 
many gene products and actions, any one of which may have only a 
subtle influence.  Accordingly, we are in the process of building up a 
sizeable collection of sarcomere-defective mutants.  A wide range of 
phenotypes including a number of temperature-sensitive mutants has 
been obtained.  We believe that only a rather complete genetic 
dissection in conjunction with detailed biochemical and structural 
studies will permit us to provide clearcut answers to such seemingly 
simple questions as 'why are there two myosins?'.