Proteomic identification and physicochemical characterisation of paramyosin and collagen from octopus ( Octopus vulgaris ) and jumbo squid ( Dosidicus gigas )

Molecular Characterization and Expression Pattern of Paramyosin in Larvae and Adults of Yesso Scallop

Simple Summary

Paramyosin is an important myofibrillar protein in smooth muscle in molluscs that is not present in vertebrate muscles. This study characterized its sequence feature and expression patterns in Yesso scallop Patinopecten yessoensis and revealed the unique phosphorylation sites in scallops. The mRNA and protein expression of paramyosin was mainly found in foot and smooth adductor muscle. At late larval stages, strong paramyosin mRNA signals were detected in the symmetric positions of anterior and posterior adductor muscles. The present findings support that paramyosin may serve as the most important component of smooth muscle assembly during muscle development and catch regulation in scallops.

Abstract

Paramyosin is an important myofibrillar protein in molluscan smooth muscle. The full-length cDNA encoding paramyosin has been identified from Yesso scallop Patinopecten yessoensis. The length of paramyosin molecule has been found to be 3715 bp, which contains an open reading frame (ORF) of 2805 bp for 934 amino acid residues. Characterization of P. yessoensis paramyosin reveals the typical structural feature of coiled-coil protein, including six α-helix (α1-α6) and one coil (η) structures. Multiple phosphorylation sites have been predicted at the N-terminus of paramyosin, representing the unique phosphorylation sites in scallops. The highest levels of mRNA and protein expression of paramyosin have been found in foot and the smooth adductor muscle. According to whole-mount in situ hybridization (WISH), strong paramyosin mRNA signals were detected in the symmetric positions of anterior and posterior adductor muscles at late larval stages. These findings support that paramyosin may serve as the most important components for myogenesis and catch regulation in scallops. The present findings will not only help uncover the potential function of myofibrillar proteins in molluscs but also provide molecular evidence to infer evolutionary relationships among invertebrates.

Effects of partial substitution of NaCl on myofibrillar protein properties from pearl mussel Hyriopsis cumingii muscle: Structural characteristics and aggregation behaviors

The effects of NaCl and its partial substitutes (KCl, MgCl₂ and CaCl₂) on solubility, structural characteristics and aggregation behaviors of myofibrillar protein (MP) from pearl mussel muscle were investigated and compared. MP at 0.6 M NaCl was beneficial to protein unfolding and showed excellent potential functional properties. When NaCl was substituted in low level, MPs also showed good solubility and ordered microstructure as well as NaCl, especially MgCl₂ and CaCl₂, due to the unfolding of α-helical structures and subsequently exposed tyrosine residues and hydrophobic groups. However, the obviously increased disulfide bonds and hydrophobic interactions in high substitution level indicated the excessive non-sodium salts had negative effects on molecular rearrangement, leading to irregular and overly tight of microstructure. Thus, NaCl partially substituted by KCl, MgCl₂ and CaCl₂ in low substitution level is promising to improve functional properties of MP in low-sodium meat products.

Identification of octopus peptide and its promotion of β-casein synthesis in a mouse mammary epithelial cell line

Octopus protein hydrolysate has been reported to increase milk yield and milk protein production. In this paper, the utilization and underlying mechanisms of bioactive peptide fractions from octopus protein hydrolysate on β-casein expression in mouse mammary epithelial cells (HC11) were investigated. Fraction OPH3-1 significantly stimulated cell proliferation and β-casein synthesis in HC11 cells, which was purified by ultra-filtration and gel-filtration chromatography. The MWs of the peptides from OPH3-1 ranged from 525-2,578 Da and consisted of 7-26 amino acid residues. Most of the peptides demonstrated the typical characteristics of milk protein synthesis promotion, especially MGLAGPR, MGDVLNF, EAPLMHV, and TEAPLMHV. Additionally, the mRNA abundances of mTOR, S6K1, 4EBP1, JAK2, and STAT5 were significantly enhanced by OPH3-1, which was consistent with the increased β-casein expression. These results suggest that the OPH3-1 peptides can promote the proliferation of mammary epithelial cells and increase β-casein synthesis. PRACTICAL APPLICATIONS: Breastfeeding mothers are generally recommended to take octopus soup as a daily diet to promote lactation. The peptides fraction OPH3-1 from the enzymatic hydrolysate of Octopus vulgaris which was revealed to significantly stimulate mammary epithelial cell proliferation and β-casein synthesis was obtained. This study suggests that octopus peptides can be used as nutritional supplements to increase the quantity and quality of milk production.