The covalent structure of cartilage collagen. Evidence for sequence heterogeneity of bovine alpha1(II) chains

During studies on the amino acid sequence of bovine nasal cartilage collagen, the cyanogen bromide peptide alpha1(II)-CB11 was degraded to smaller peptides with trypsin. One of the tryptic peptides, T5, which contained 39 residues was shown by amino acid and sequence analyses to occur in a predominant form that contained glutamine at position 5 and in a second form with leucine at this site. In addition to the heterogeneity at this position, amino acid analyses of five different preparations revealed that the peptide with leucine contained a seryl residue not found in the major form. Sequence heterogeneity at a third position of alpha1(II) was demonstrated by the isolation of a hexapeptide (T2) from the trypsin digest of alpha1(II)-CB11 which contained 0.21 residue of alanine and 0.77 of leucine. Both the leucine and alanine of T2 were removed after the second cycle of subtractive Edman degradation. These data show that at least two types of alpha1(II) chains, designated as alpha1(II)Major and alpha1(II)Minor, exist in bovine nasal cartilage. Further considerations suggest that these two chains are probably not variants derived from allelic genes but are the products of separate genes.