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.
Highlights
Paramyosin is a protein found exclusively in invertebrate muscles [1] [2]
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
Using this cDNA as a template, PCR was performed with the primers designed from paramyosin sequences of oyster, octopus, abalone, and mussels, as previously reported, to obtain the internal sequence of squid paramyosins (Figure 1, Table 1)
Summary
Paramyosin is a protein found exclusively in invertebrate muscles [1] [2]. Para-. As the muscle of squid is covered by four layers of skin and is tough in texture when eaten in raw, it is often prepared by scoring the surface with a knife [9] It can be highly processed into a product that is similar to fish paste, so that it is more soft and easier to chew for people of all ages. The other aspect is the unique texture of squid paste compared to that of fish paste This difference in texture has been suggested to be attributable to paramyosins present in invertebrate meats. The determination of the primary structures of squid paramyosin is possibly available for understanding the reason of the species-specific food processing. The present study was conducted with the aim of determining the primary structure of paramyosins from the mantles of edible squid species, including three species in the order Teuthida and one species in the order Sepiida, as well as characterizing the squid paramyosins
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