Identification and primary structures of eel type I collagen pro alpha 1, pro alpha 2 and pro alpha 3

摘要

Many bony fish type I collagens have a characteristic third chain designated as alpha 3(I). However, much less is known about the primary structure and distinction of the pro alpha(I) chains. Their cDNAs were cloned by RT-PCR from the muscle tissue of Japanese eel, Anguilla japonica. Three cDNAs coding for the triple-helical domain of fibrillar collagen were identified as pro alpha 1(I), pro alpha 2(I) and pro alpha 3(I) chains by sequencing selected tryptic peptides isolated from eel type I collagen subunit chains, alpha 1(I), alpha 2(I) and alpha 3(I). Eel pro alpha 3(I) had high amino acid sequence identity (81 ) to its pro alpha 1(I). The distribution of seven Cys residues in the C-propeptide of pro alpha 3(I) was identical to that of pro alpha 1(I). There was a third Cys residue at the 1,268th position from the N-terminus in pro alpha 1(I), though a supposed Cys residue at the 1,264th position in pro alpha 3(I) was replaced by a Ser residue. Similar replacement has been observed in the pro alpha 3(I) chains of trout and zebrafish. These combined results suggest that replacement of the Cys residue allows for the identification of fish collagen pro alpha(I) previously not identified as pro alpha 3(I).