Processing of type XI collagen. Determination of the matrix forms of the alpha1(XI) chain.
Type XI collagen is mainly found as a minor constituent in type II-containing fibrils and presents a alpha1(XI)alpha2(XI)alpha3(XI) stoichiometry. This molecule was shown to be partially processed in its intact tissue form. Moreover, alternative splicing has been demonstrated in the variable region of the N-terminal domain of alpha1(XI) and alpha2(XI) chains. In this work, the processing of a major intact form of alpha1(XI) from matrix laid down by chick chondrocytes in culture was identified using N-terminal sequencing and antibodies to synthetic peptides corresponding to the N-terminal propeptide cDNA-derived sequence. The results show that the fully processed form of alpha1(XI) begins at Gln254 of the N-terminal propeptide, seven residues before the end of the proline/arginine-rich protein region encoded by exon I (Zhidkova, N. I., Justice, S. K., and Mayne, R. (1995) J. Biol. Chem. 270, 9486-9493). This sequence is immediately followed by a sequence encoded by exon III. The processing takes place at an Ala-Gln sequence that corresponds to a consensus sequence for procollagen N-proteinase. The antibody raised against a sequence located within the region corresponding to exon IV (anti-P8) fails to recognize this fully processed form of the alpha1(XI) chain. It recognizes, however, two minor bands of high molecular mass. These results suggest that a major cartilage form of alpha1(XI) is the product of alternative splicing in which sequences encoded by both exons II and IV are skipped. The presence of a highly acidic subdomain encoded by exon III at the N terminus of the major form of the alpha1(XI) chain, as predicted by these data, provides potential sites for interaction of collagen XI with other molecules.
Rousseau
J C
JC
Institut de Biologie et Chimie des Protéines, UPR412 CNRS, 7 Passage du Vercors, F-69367 Lyon Cedex 7, France.
Farjanel
J
J
Boutillon
M M
MM
Hartmann
D J
DJ
van der Rest
M
M
Moradi-Améli
M
M
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D002645:Chickens; D003094:Collagen / Q000235:genetics / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D011499:Protein Processing, Post-Translational; D051381:Rats; D016415:Sequence Alignment
D016326:Extracellular Matrix Proteins; D010446:Peptide Fragments; D010455:Peptides; D003094:Collagen