Peptide mapping of cornea collagens from chick embryos by dodecylsulfate/polyacrylamide gel electrophoresis

Using differential salt fractionation, different collagen types were obtained from corneas of 17-day-old chick embryos. The collagen precipitated by 1.7 M and 2.5 M NaCl consisted of type I collagen, having an alpha 1: alpha 2 ratio of 2. The collagen precipitated by 5 M NaCl contained alpha A, alpha B, alpha 1 and alpha 2 chains having an alpha A: alpha B ratio of 1 and an alpha 1: alpha 2 ratio of 10. The alpha 1 and alpha 2 chains isolated from corneas were found to have higher mobility in polyacrylamide gel electrophoresis in sodium dodecylsulfate as compared with that of their counterparts isolated from embryonic chick tendons. When the alpha 1 and alpha 2 chains isolated by polyacrylamide gel electrophoresis in sodium dodecylsulfate were subjected to limited protease degradations, the peptide maps obtained from corneal alpha chains were not identical to those of tendon alpha chains. It is suggested that the type I collagen in cornea is different from type I collagen in tendon. Also the results indicated that the alpha 1 chain present in the 5 M NaCl precipitate is a type I alpha 1 chain.