Molluscan smooth catch muscle contains calponin but not caldesmon

Abstract

We isolated Ca(2+)-regulated thin filaments from the smooth muscle of the mussel Crenomytilus grayanus and studied the protein composition of different preparations from this muscle: whole muscle, heat-stable extract, fractions from heat-stable extract, thin filaments and intermediate stages of thin filaments purification. Among the protein components of the above-listed preparations, we did not find caldesmon (CaD), although two isoforms of a calponin-like (CaP-like) protein, which along with CaD is characteristic of vertebrate smooth muscle, were present in thin filaments. Thus, CaD is not Ca(2+)-regulator of thin filaments of this muscle. On the other hand, the mussel CaP-like protein is also not such Ca(2+)-regulator since we have shown that this protein can be selectively removed from isolated mussel thin filaments without loss of their Ca(2+)-sensitivity. We suggest that thin filaments in the smooth catch muscle possess other type of Ca(2+)-regulation, different from that in vertebrate smooth muscles.

Molecular characterization of calponin in the catch muscle of the Yesso scallop Mizuhopecten yessoensis

“…2) [28]. It has been reported that mussel calponin inhibits Mg 2+ -ATPase activity in catch muscle actomyosin [6,7]. These findings suggest that molluscan calponin might regulate muscle contraction in a similar way to vertebrate smooth muscle.…”

Hybrid and non-hybrid actomyosins reconstituted with actin, myosin and tropomyosin from skeletal and catch muscles

“…So, the situation appears to be more complicated: the differences in the degree of activation might be attributed to both the myosin component and the actin component. The actin-binding proteins of mussel thin filaments are tropomyosin, calponin, troponin components and a few non-identified minor polypeptide [8,13]. Testing of the proteins listed above has revealed that the inhibiting effect is exerted by mussel tropomyosin.…”

“…Mussel thin filaments, mussel myosin and mussel tropomyosin were prepared as described previously [8,10]. The rabbit skeletal muscle actin of Straub type was prepared according to Rees and Yang [11], rabbit skeletal muscle myosin was prepared according to Margossian and Lowey [12].…”

“…Some hybrid models, including proteins of the catch muscle of bivalves, possess unusual properties; molluscan tropomyosin -as a component of such models -inhibits their ATPase activity [6,7]. Also, hybrid models incorporating native mussel thin filaments have low ATPase activity [8]. It is assumed that these unusual properties are associated with peculiarities of the Ca 2þ -regulatory system of bivalve's muscle thin filaments, which belongs to the "accelerator type" compared with the vertebrate skeletal muscle system that has the "brake-type" property [9].…”

Natural Actin and Tropomyosin from Molluscan Catch Muscle

“…Both catch hypotheses involve participation of thin filaments in this phenomenon. To date, the composition of proteins in thin filaments of the catch muscle is fairly well studied [8], and methods have been developed for isolation of these proteins: natural actin [9], tropomyosin [10], troponin [11], calponin [12], filamin [13], α-actinin [14]. In this work, we isolated and purified the main proteins of thin filaments, actin and tropomyosin, from the catch muscle of bivalve and from the skeletal muscles of vertebrates.…”