Synthesis of lens protein in vitro: formation of beta-crystallin

Upon addition of lens polyribosomes to a reticulocyte-cell-free system, alpha, beta L-, and gamma crystallin are synthesized, while beta H crystallin is not formed. This phenomenon is comparable to the biosynthetic events in the lens-cell-free system and in tissue culture. It is shown that beta H crystallin formation depends upon the presence of a polypeptide beta B1 b which arises by posttranslational modification. The putative precursor for beta B1 b is a polypeptide beta BU a of which the messenger with a sedimentation coefficient of 12.5 S has been isolated.