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.
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.