Effect of temperature on the actomyosin‐paramyosin structure from giant squid mantle (Dosidicus gigas)

Abstract

BACKGROUND: The secondary structure of a protein determines its functional properties, such as its gelling capacity. The -helix and -sheet comprise its main structures. Myofibrillar proteins from jumbo squid are composed mainly of the actomyosin-paramyosin complex; this complex contains a high percentage of -helix, because actin, paramyosin, and myosin constitute 30%, 100%, and 55% of the -helix, respectively. It is important to elucidate the role of the secondary structures in the gelation of giant squid proteins as they form gel. The role of the secondary structures in the gelation of giant squid proteins is therefore very important. For this reason, the objective of this work was to evaluate the effect of temperature on the structural behavior of actomyosin-paramyosin isolate (API) from Dosidicus gigas. RESULTS:The unfolding of the API system, which is composed of the actomyosin-paramyosin complex, was clarified by studying surface hydrophobicity and viscosity. Three characteristic peaks were found, associated with myosin, paramyosin, and actin. Infrared and circular dichroism corroborated the view that API undergoes major structural changes, because it proceeds from mostly an -helix structure to 100% -sheet. CONCLUSION: The structural rearrangement favors gelation by cross-linking, generating new protein-protein and water-protein interactions, which create a more stable structure compared to mantle proteins (MP). Likewise, the presence of sarcoplasmic and stromal proteins in D. gigas muscle prevents the unfolding of myofibrillar proteins, favoring gelation by agglomeration, decreasing the ability to trap water and thus its gelling capacity.

The influence of KCl concentration on the gelation of myofibrillar protein giant squid (Dosidicus gigas) due to molecular conformation change

“…The salt concentration range covers protein responsibility from no effect to pure screening effect and then to conformation change. The studying temperature was stopped at 45°C because myofibrillar protein molecules denaturation mostly occurred under this value in the heating gelation process ( 9 ). This study aims at understanding the mechanism of the KCl effect on paramyosin interactions, thereby probing this protein molecule conformation change under various KCl concentrations.…”