CHANGES OF CARP MYOSIN SUBFRAGMENT-1 INDUCED BY TEMPERATURE-ACCLIMATION

Heavy meromyosin subfragment-1 (S1) was prepared by alpha-chymotrypsin from myosin of carp acclimated to either 10-degrees-C or 30-degrees-C for a minimum of 5 weeks. The objective of these studies was to document thermally-induced changes in the myosin molecule and to extend previous observations. Ca2+- and K+ (EDTA)-ATPase activities of cold-acclimated carp S1 were 1.1 and 0.8-mu-mol P(i).min-1.mg-1, respectively, and these values did not differ significantly from those of warm-acclimated carp. The inactivation rate constant (K(D)) of S1 from cold-acclimated carp was 32.1 x 10(-4).s-1, compared to 13.2 x 10(-4).s-1 for warm-acclimated carp. The maximum initial velocity of acto-S1 Mg2+- ATPase activity at pH 7.0 in 0.05 M KCl was 9.3 s-1 with cold-acclimated carp, about 3.7 times higher than that for warm-acclimated carp. However, no significant difference was observed in the apparent affinity of S1 to actin. Peptides maps of the heavy chain of S1 were different and suggested distinct isoforms for the myosins from warm- and cold-acclimated muscle.