Studies on the assembly of the rat lens capsule. Biosynthesis and partial characterization of the collagenous components

Abstract

Isolated rat lens capsules synthesized hydroxy[3H]proline-containing polypeptides when incubated with [3H]proline. The collagenous polypeptides synthesized during a 2 h incubation were analyzed by gel filtration chromatography and sodium dodecyl sulfate/polyacrylamide gel electrophoresis and shown to have an apparent MW of .apprx. 180,000. No evidence was obtained for conversion of these polypeptides into a lower-MW species in experiments where capsules were labeled for 2 h and chased with non-radioactive proline for up to 22 h. A time-dependent incorporation of the 180,000 MW species into a larger collagenous component was observed and this could be prevented by the inclusion of .beta.-aminopropionitrile in the incubation medium. The radioactive components synthesized by the capsules correspond to subunits of the intact lens capsule and the direct incorporation of the polypeptide of MW 180,000 into deoxycholate-insoluble basement membrane was demonstrated.