Catch muscle myorod modulates ATPase activity of Myosin in a phosphorylation-dependent way.

Oleg S Matusovsky,Galina G Matusovskaya,Apolinary Sobieszek,Anna V Dobrzhanskaya,Nikolay S Shelud’Ko,Ulyana V Shevchenko,L Michel Espinoza-Fonseca

doi:10.1371/journal.pone.0125379

Abstract

Myorod is expressed exclusively in molluscan catch muscle and localizes on the surface of thick filaments together with twitchin and myosin. Myorod is an alternatively spliced product of the myosin heavy-chain gene that contains the C-terminal rod part of myosin and a unique N-terminal domain. The unique domain is a target for phosphorylation by gizzard smooth myosin light chain kinase (smMLCK) and, perhaps, molluscan twitchin, which contains a MLCK-like domain. To elucidate the role of myorod and its phosphorylation in the catch muscle, the effect of chromatographically purified myorod on the actin-activated Mg2+-ATPase activity of myosin was studied. We found that phosphorylation at the N-terminus of myorod potentiated the actin-activated Mg2+-ATPase activity of mussel and rabbit myosins. This potentiation occurred only if myorod was phosphorylated and introduced into the ATPase assay as a co-filament with myosin. We suggest that myorod could be related to the catch state, a function specific to molluscan muscle.

Highlights

The smooth muscle of molluscs exhibit the so-called “catch state”, where high tension is maintained for a long time with little expenditure of energy
We further demonstrated that the formation of co-filaments assembled from myosin and phosphorylated myorod is a precondition for the potentiation of myosin Mg2+-ATPase activity
CF1 strongly increased Mg2+-ATPase activity of AM formed from skeletal myosin and Factin, whereas CF2 activated myosin’s ATPase significantly less than CF1 (Fig 2)

Summary

Introduction

The smooth muscle of molluscs exhibit the so-called “catch state”, where high tension is maintained for a long time with little expenditure of energy. Molluscan smooth muscle contains a unique composition of thick filament-associated proteins. The major component of large diameter molluscan thick filaments is paramyosin whose surface is covered with myosin [1], twitchin [2, 3] and myorod [4]. A water-insoluble, heat-resistant protein consists of two polypeptides of 112 and 120 kDa [4, 7], is an alternative product of the myosin heavy-chain gene. It contains a C-terminal rod part, which is identical to the rod portion of myosin, and a unique N-terminal domain [8]. The identity of the C-terminal parts and the similarity between the domain structures of myosin and myorod [9] suggest that myorod is integrated into the surface of the paramyosin core

Methods

Results

Conclusion