Genetic variants of the Bombyx mori silkworm encoding sericin proteins of different lengths

Abstract

A variant sericin polypeptide originally found by acid gel electrophoresis in the Nd-s mutant strain of the silkworm, Bombyx mori, has been analyzed genetically. The variant polypeptide (called S-2v) is encoded by a gene which behaves as a codominant allele of the gene encoding the standard S-2 sericin polypeptide. Linkage analysis locates these alleles at 0.0 map unit on chromosome 11. SDS-polyacrylamide gel electrophoresis shows that the molecular weight of the S-2v variant polypeptide is lower by approximately 62,500 than that of the S-2 polypeptide. Amino acid analysis indicates that the two sericin polypeptides have similar compositions. These results are consistent with the idea that the variant allele arose by deletion within the S-2 coding sequence in the Src-2 gene locus as the result of unequal recombination.

Studies on middle and posterior silk glands of silkworm (Bombyx mori) using two-dimensional electrophoresis and mass spectrometry

“…Sericins, which coat the silk core, are secreted exclusively by the MSG, the thickest part of the silk gland. At least six glycoproteins encoded by the sericin 1 and sericin 2 genes have been found in B. mori (Grzelak, 1995;Gamo, 1982;Michaille et al, 1986). The longest suborgan, the PSG, is responsible for the synthesis of the silk core protein fibroin, which first moves to the MSG where molecules of sericin are added, then toward the ASG where the silk fiber is formed and spun (Inoue et al, 2000).…”

Use of Silk Protein, Sericin, as a Sustained-Release Material in the Form of a Gel, Sponge and Film

“…The structural analysis and cloning of SC genes Ser1 and Ser2 (Src-2) have been described. [3][4][5][6] Correspondence of the amino acid composition of SC with these genes suggested that the 150-and 400-kDa SCs correspond to Ser1 proteins (77-331 kDa) encoded by the Ser1 gene, and that the 250-kDa SC corresponds to S-2 protein (227 kDa) encoded by the Src-2 gene.2) The most abundant component is the largest SC (400 kDa), which corresponds to the Ser1C protein (331 kDa).2) A repetitive 38-amino acid sequence rich in Ser (40%) dominates a large part of the Ser1C protein and is predicted to have a strong tendency to form b-sheet structure. Another part of the Ser1C protein is hydrophilic and has a high content of charged residues including acidic (glutamic acid (Glu) and Asp) and basic (lysine (Lys) and arginine (Arg)) amino acids.…”

“…The structural analysis and cloning of SC genes Ser1 and Ser2 (Src-2) have been described. [3][4][5][6] Correspondence of the amino acid composition of SC with these genes suggested that the 150-and 400-kDa SCs correspond to Ser1 proteins (77-331 kDa) encoded by the Ser1 gene, and that the 250-kDa SC corresponds to S-2 protein (227 kDa) encoded by the Src-2 gene.…”

A novel variant of acid phosphatase isozyme from hemolymph of the silkworm, Bombyx mori.

“…Electrophoretic variants are widespread in the silkworm, Bombyx mori (Yoshitake and Akiyama, 1964;Eguchi et al, 1965Eguchi et al, , 1984Eguchi and Yoshitake, 1967;Gamo, 1968Gamo, , 1978Gamo, , 1982 as well as other animals. It is noteworthy, however, that the phosphatase E is an isozyme showing different properties, that is, acid phosphatase isozymes would comprize heterogeneity not only in non-catalytic sites but also in the catalytic site.…”