Embryonic neural retina collagen: In vitro synthesis of high molecular weight forms of type II plus a new genetic type

Abstract

Chicken neural retina cells from 6 to 7 day old embryos were labeled with [3H]proline for 24 and 72 h, and the collagenous proteins of the medium were analyzed. Ninety percent of the collagenous proteins eluted from DEAE-cellulose columns as a peak near the middle of the gradient. Upon sodium dodecyl sulfate/polyacrylamide gel electrophoresis, this material consisted predominantly of a slowly migrating procollagen, a smaller amount of an intermediate migrating form and some .alpha.-chain material. Limited enzymatic digestion of this DEAE peak material plus mapping of its CNBr peptides identified this material as a type II precursor. The remaining 10% of the collagenous proteins eluted from DEAE-cellulose at the end of the gradient. Electrophoresis of this fraction showed 4 major bands. Two migrated near the type II precursors, a 3rd migrated somewhat more slowly and the 4th was near .beta.-chain dimers. There was 2 minor bands. Limited pepsin digestion of this DEAE peak material produced 2 bands: one migrated slightly more slowly than .alpha.1 and the second, considerably more slowly. The CNBr peptide pattern of this material appears to be different from any previously described. Neural retina cells in culture synthesize at least 2 genetically distinct classes of collagenous proteins. One represents precursors to type II. The second is composed of multiple, very high MW forms which may represent precursors (procollagens) of a new genetic type(s) of collagen.