title: Primary structure of the silk fibroin light chain determined by cDNA sequencing and peptide analysis.
abstract: A cDNA clone, pFL18, carrying a putative full-length fibroin light chain (L-chain) sequence was isolated and its nucleotide sequence was determined. This revealed the presence of an open reading frame corresponding to a polypeptide with 262 amino acid residues. The sequence was concluded to be that of the L-chain with its signal peptide because corresponding amino acid sequences for the seven tryptic and the four chymotryptic peptides from the purified L-chain were all included and an N-terminal region having typical properties of a signal peptide was present. The N terminus of the mature form of L-chain was identified as N-acetyl serine by analyzing the acyl-dansylhydrazide derived from the N-acyl-amino acid which had been released from the N-terminal blocked chymotryptic peptide by the acylamino acid-releasing enzyme. It was suggested that a signal peptide had cleaved between Pro18 and Ser19, yielding a mature L-chain polypeptide consisting of 244 amino acid residues. The molecular weight of the L-chain was calculated to be 25,800 including the N-acetyl group. The L-chain contained three Cys residues, two of which were suggested to form an intramolecular disulfide linkage, leaving the third one at the most C-terminal position and in a relatively hydrophilic region as the most probable site of disulfide linkage with the fibroin heavy chain.
authors.affiliation: Department of Agricultural Chemistry, Faculty of Agriculture, Tohoku University, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Kikuchi
authors.forename: T
authors.initials: T
authors.lastname: Takagi
authors.forename: A
authors.initials: A
authors.lastname: Kikuchi
authors.forename: F
authors.initials: F
authors.lastname: Oyama
authors.forename: K
authors.initials: K
authors.lastname: Shimura
authors.forename: S
authors.initials: S
authors.lastname: Mizuno
mesh_terms: D000581:Amidohydrolases; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx; D002918:Chymotrypsin; D003001:Cloning, Molecular; D004247:DNA; D005349:Fibroins / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011061:Poly A / Q000235:genetics; D011487:Protein Conformation; D021382:Protein Sorting Signals / Q000235:genetics; D015183:Restriction Mapping; D014357:Trypsin
chemical_list: D021382:Protein Sorting Signals; D011061:Poly A; D004247:DNA; D005349:Fibroins; D002918:Chymotrypsin; D014357:Trypsin; D000581:Amidohydrolases; C032846:alpha-N-acylamino acid hydrolase