Amino-terminal propeptide of human pro-alpha 2(V) collagen conforms to the structural criteria of a fibrillar procollagen molecule

We have determined the nucleotide sequence of a cDNA clone encoding the amino-terminal portion of human alpha 2(V) procollagen and found that the structure of the 186-residue amino-terminal propeptide closely resembles those of the fibril-forming procollagens. Juxtaposed to a 26-residue leader peptide, pro-alpha 2(V) exhibits a characteristic cysteine-rich globular region followed by 24 Gly-X-Y repeats which are interrupted by two short non-collagenous sequences. Upon closer examination, each of these two sequences was noted to display structural motifs characteristic of either pro-alpha 1(I) and pro-alpha 1(III) collagens or pro-alpha 1(II) collagen, respectively. Finally, within the amino-terminal telopeptide, a putative amino-terminal proteinase cleavage site, Ala-Gln, was identified. This latter finding strongly suggests that the alpha 2(V) amino-terminal propeptide can be potentially processed and thus leaves unresolved the issue pertaining to the nature of the collagenase-resistant sequence that is retained by mature type V collagen molecules.