Worm Breeder's Gazette 6(1): 34

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.

Characterization and Roles of Calmodulin and a Second Calcium Regulatory Protein from C. elegans

F.H. Schachat, D.D. Bronson, G.A. Jamieson Jr., T.C. Vanaman

In these studies we have purified and characterized two proteins 
involved in Ca-regulation in Caenorhabditis 
st is calmodulin (CaM) which is considered to 
be an intracellular receptor for calcium because of the large number 
of cellular processes it activates in a Ca-dependent manner.  The 
second protein which is similar to CaM in many of its physical and 
chemical properties, we have called the troponin-C like protein (TnCLP)
Because of a report which suggested invertebrate CaMs are dissimilar 
to those of vertebrates our studies on C.  elegans CaM have focused on 
a comparison of its properties to those of bovine brain CaM.  The C.  
elegans protein shows no major difference in amino acid composition, 
cyanogen bromide (CNBr) peptide maps, electrophoretic behavior or 
enzymatic properties in those studies.
The C.  elegans TnCLP, which copurifies with the CaM until DE-52 ion 
exchange chromatography, can be distinguished from CaM.  It differs in 
amino acid composition, CNBr peptide maps and molecular weight, and 
lacks the ability to activate bovine brain cyclic nucleotide 
phosphodiesterase.  Our concern with it has centered about defining 
its possible physiological roles.  TnCLP forms Ca-dependent complexes 
with rabbit fast skeletal muscle troponin I and troponin T.  It 
copurifies with thin myofilaments.  These observations coupled with 
its inability to activate bovine brain cyclic nucleotide 
phosphodiesterase suggest that C.  elegans TnCLP is not a second 
generalized Ca-dependent activator like CaM, but functions as a 
troponin C.
We believe that the C.  elegans TnCLP and CaM are responsible for 
the 2 thin and thick myofilament Ca-regulation that has been reported 
in C.  elegans.  The TnCLP acting in a troponin-like complex to 
regulate thin filaments.  The CaM acting on thick filaments through a 
myosin light chain kinase as has been reported for other actomyosin 
contractile systems.  In support of that later contention we have 
shown that there is an in vitro Ca and CaM dependent phosphorylation 
of one of the C.  elegans myosin light chains.
We expect these studies will serve as the basis for elucidating the 
Ca-dependent events in muscle contraction (as well as in other 
processes) both in vivo and in vitro through the analysis of genetic 
variants of C.  elegans that may be blocked in different steps or 
pathways of Ca-regulation.