cDNA Cloning of Paramyosin from Several Kinds of Squid Mantle Muscle

Abstract

Paramyosin is a rod-shaped muscle protein found exclusively in invertebrates, with α-helices coiled around each other to form a coiled-coil structure. Marine organisms in which the primary structure of paramyosin has been determined are mollusks, including abalone (Haliotis discus), mussels (Mytilus galloprovincialis), octopus (Octopus bimaculoides), and oyster (Crassostrea gigas). In contrast, the primary structure of squid paramyosin, which is of particular interest, has yet to be reported. In the present study, cDNA cloning of paramyosins from four squid species, the neon flying squid (Ommastrephes bartramii), the Humboldt squid (Dosidicus gigas), the golden cuttlefish (Sepia esculenta), and the clawed armhook squid (Gonatus onyx), was performed to determine the following: the 2605-bp O. bartramii paramyosin gene containing a 2574-bp open reading frame (ORF), the 2691-bp D. gigas paramyosin gene containing a 2640-bp ORF, the 2631-bp S. esculenta paramyosin gene containing a 2574 ORF, and the 2609-bp G. onyx paramyosin gene containing a 2574-bp ORF. The primary structure of the four squid paramyosins was found to contain heptad repeats and an ACD (assembly competence domain), which are characteristic of a coiled coil. A phylogenetic analysis was performed with paramyosin sequences from species including the four squid species examined in this study, the results of which indicated that the four squid paramyosins form a group independent from the paramyosins of other species, to which octopus paramyosins are closest.

Biochemical and physicochemical characteristics of the major muscle proteins from fish and shellfish

“…For example, the top shell muscle and oyster adductor muscle contain around 40%, while the scallop adductor (smooth muscle) and octopus arm contain around 30% (Ochiai et al 1985;Watabe et al 1986) of paramyosin against the total myofibrillar protein. Paramyosin is a dimer of approximately 100 kDa subunits and forms a coiled-coil structure like the myosin rod (Watabe and Iwasaki 2000;Kajita et al 2018). This protein also forms a thick filament under physiological ionic strength and is localized at the core of the invertebrate thick filament, where myosin molecules cover the surface (Oiwa et al 1998).…”