Isolation and characterization of a cDNA clone for the amino-terminal portion of the pro-alpha 1(II) chain of cartilage collagen.

We have isolated a cDNA clone (pRcol 2) which is complementary to the 5'-terminal portion of the rat pro-alpha 1(II) chain mRNA. A synthetic oligonucleotide was used both as a primer for cDNA synthesis and as a probe for screening a cDNA library. The probe was a mixture of sixteen 14-mers deduced from an amino acid sequence present in the amino-terminal telopeptide of the rat cartilage alpha 1(II) chain. This primer was chosen so that the resulting cDNA would contain the sequence of the 5' end of the mRNA. The nucleotide sequences of the cDNA were determined and compared with that of three other interstitial procollagen chain mRNAs (pro-alpha 1(I), pro-alpha 2(I), and pro-alpha 1(III) chain mRNA). pRcol 2 contains a 521-base pair (bp) insert, including 153 bp of the 5' untranslated region plus 368 bp coding for the signal peptide, the amino-terminal propeptide, and a part of the telopeptide. The signal peptide of the type II collagen chain is composed of about 20 amino acids. There is little homology between the amino acid sequence of the signal peptide in the pro-alpha 1(II) chain and that of three other interstitial procollagen chains. The NH2-terminal propeptide is deduced to contain short nonhelical sequences at its amino and carboxyl ends and an internal helical collagenous domain comprising 25 repeats of Gly-X-Y with one interruption. There is a strong conservation of the amino acid sequence of the carboxyl-terminal part of the NH2-terminal propeptide in the pro-alpha 1(II), pro-alpha 1(I), and pro-alpha 2(I) chains. Type II collagen mRNA does not contain a sequence corresponding to a uniquely conserved nucleotide sequence around the translation initiation site which occurs in mRNA for other procollagen chains.