Homologous regions of collagen alpha1(I) and alpha1(II) chains: apparent clustering of variable and invariant amino acid residues

LC-MS/MS identification of the O-glycosylation and hydroxylation of amino acid residues of collagen α-1 (II) chain from bovine cartilage

O-Glycosylation of collagen is a unique type of posttranslational modifications (PTMs) involving the attachment of galactose (Gal) or glucose-galactose (Glc-Gal) moieties to hydroxylysine (HyK). Also, hydroxyproline (HyP) result from the posttranslational hydroxylation of some proline residues in collagen. Here, LC-MS/MS was effectively employed to identify 23 O-glycosylation sites and a large number of HyP residues associated with bovine type II collagen α-1 chain (CO2A1). The modifications of the 23 O-glycosylation sites varied qualitatively and quantitatively. Both Gal and Glc-Gal moieties occupied 22 of the identified glycosylation sites, while K773 was observed as unmodified. A large number of HyP residues at Yaa positions of Gly-Xaa-Yaa motif were detected. HyP residues at Xaa positions of Gly-HyP-HyP, Gly-HyP-Ala, and Gly-HyP-Val motifs were also observed. Notably, HyP residue of Gly-HyP-Gln motif was detected, which has not been previously reported. Moreover, the deamidation of 8 Asn residues was identified, of which 2 Asp residues were observed at different retention times because of isomerization (Asp vs isoAsp). Partial macroheterogeneities of some CO2A1 glycosylation sites were revealed by LC-MS/MS analysis. ETD experiments revealed partial macroheterogeneities associated with K299-K308, K452-K464, K464-K470, and K857-K884 glycosylation sites. Semiquantitative data suggest that the glycosylation of hydroxylysine residues is site-specific.

Molecular definition and characterization of recombinant bovine CB8 and CB10: immunogenicity and arthritogenicity

Theoretically, the ability to produce recombinant type II collagen (CII) peptide fragments in a prokaryotic expression system would be extremely useful for preparing adequate amounts of CII peptides suitable for therapeutic uses. Bacteria do not contain the enzymes involved in the extensive posttranslational modifications that occur during the biosynthesis of CII, such as the hydroxylation of prolyl and lysyl residues and glycosylation of hydroxylysyl residues. As these posttranslational modifications may play a role in the immune and arthritogenic response to CII, it was unclear whether collagen expressed in Escherichia coli would be immunologically comparable to tissue-derived CII. Therefore, we prepared recombinant proteins for CB8 and CB10 by cloning CB8 (CII 403-551) and CB10 (CII 552-897) genes from bovine chondrocytes by RT-PCR technique and expressing them in an E. coli expression system. Characterization of these recombinant proteins revealed that both rCB8 and rCB10 stimulated T cell proliferation in a T cell determinant-specific manner. The T cells from mice immunized with rCB8 respond specifically to a synthetic peptide, CII 445-453, the CB8 T cell determinant. Conversely, rCB10-primed T cells respond strongly to CII 610-618, the CB10 T cell determinant. Recombinant CB8-induced autoantibodies that bound to mouse CB8 as effectively and in the same topographic distribution as tissue-derived CB8. Finally, when rCB8 and rCB10 proteins were used to immunize B10.RIII (H-2(r)) mice, rCB8 induced arthritis in 33% of the mice, very similar to the incidence induced by tissue-derived CB8 peptide. As was found to be the case with tissue-derived CB10, rCB10 was completely ineffective in inducing arthritis. Pathological changes of arthritic joints in the mice immunized with rCB8 were similar to those observed in mice immunized with tissue-derived CB8. Thus, these recombinant CII peptides expressed in E. coli can induce an effective immunologic response and suggest that functionally useful CII peptides can be generated by the prokaryotic expression system.

Structure of cDNA clones coding for human type II procollagen. The alpha 1(II) chain is more similar to the alpha 1(I) chain than two other alpha chains of fibrillar collagens

Overlapping cDNA clones were isolated for human type II procollagen. Nucleotide sequencing of the clones provided over 2.5 kb of new coding sequences for the human pro alpha 1(II) gene and the first complete amino acid sequence of type II procollagen from any species. Comparison with published data for cDNA clones covering the entire lengths of the human type I and type III procollagens made it possible to compare in detail the coding sequences and primary structures of the three most abundant human fibrillar collagens. The results indicated that the marked preference in the third base codons for glycine, proline and alanine previously seen in other fibrillar collagens was maintained in type II procollagen. The domains of the pro alpha 1(II) chain are about the same size as the same domains of the pro alpha chains of type I and type III procollagens. However, the major triple-helical domain is 15 amino acid residues less than the triple-helical domain of type III procollagen. Comparison of hydropathy profiles indicated that the alpha chain domain of type II procollagen is more similar to the alpha chain domain of the pro alpha 1(I) chain than to the pro alpha 2(I) chain or the pro alpha 1(III) chain. The results therefore suggest that selective pressure in the evolution of the pro alpha 1(II) and pro alpha 1(I) genes is more similar than the selective pressure in the evolution of the pro alpha 2(I) and pro alpha 1(III) genes.

Covalent structure of collagen. Amino acid sequence of an arthritogenic cyanogen bromide peptide from type II collagen of bovine cartilage

Bovine articular type II collagen was prepared by limited pepsin digestion, differential salt fractionation and carboxymethylcellulose chromatography. Cyanogen bromide digestion of purified type II collagen alpha chains yielded twelve distinct peptides designated CB1-12. The peptide alpha 1(II)-CB11 was isolated by carboxymethylcellulose chromatography and Sephadex G-75S gel filtration. Automated Edman degradation together with chymotrypsin, thermolysin and trypsin digestion enabled identification of its complete amino acid sequence. Compared with type I and type III collagen, the data show similarity with alpha 1(I)-CB8 and alpha 1(III)-CB6-1-8-10-2 peptides, respectively. The peptide is located within residues 124-402 of the alpha 1(II) collagen chain and with its identification, now extends the known amino acid sequence of bovine type II cartilage collagen to 660 amino acid residues including alpha 1(II)-CB1-2-6-12-11-8-10 (partial). This corresponds to alpha 1(I)-CB0-1-2-4-5-8-3-7 (partial; 1-660) and alpha 1(III)-CB3A-3B-3C-7-6-1-8-10-2-4-5 (partial; 1-660) of bovine alpha 1(I) and alpha 1(III) collagen chains.

Biochemical characteristics and biological significance of the genetically-distinct collagens

In recent years it has become evident that genetic polymorphism is dramatically expressed in the structural protein, collagen. Current information on the biochemical properties, biosynthesis, and tissue distribution of Type I, II, and III collagens is summarized with special reference to possible unique functional roles fulfilled by each of these collagens.