Chick proα2 (I) collagen gene; exon location and coding potential for the prepropeptide

Abstract
We report the DNA sequence of a cDNA clone complementary to the 5′ end of the chick proα2(I) mRNA. The sequence enables us to deduce the and no acid sequence of this region, which has been refractory to conventional protein sequencing techniques. Its importance lies in the role of the prepropeptide in secretion, triple helix formation of the mature protein and initiation of flbrillogenesis. We have also located four of the five exons which code for this region on the genome. One exon is only llbp in size and appears to code exclusively for the signal propeptidase cleavage site. This is an extreme example of an exon defining a functional unit.