Proteolytic substructure of myorod, a thick filament protein of molluscan smooth muscles

Myorod (MR), a new thick filament protein,of molluscan smooth muscles, is an alternatively spliced product of the myosin NO heavy chain gene. We studied digestion of MR and Mn from the posterior adductor of Crenomytilus grayanus and the outer portion of adductor of Mizuchopecten (Patinopecten) yessoensis by papain and constructed the proteolytic substructure of MR, that is an analogue to Mn substructure. There are a head domain (analogue of Mn SI) and a rod domain (analogue of Mn rod); the junction between them is split at low ionic strength. The rod, in turn, consists of a neck domain (analogue of Mn S2) and a tail domain (identical to light meromyosin); the junction between them is split at high ionic strength. The localization and possible function of MR are discussed. (C) 2002 Elsevier Science Inc. All rights reserved.