Synthesis of Lens Protein <em>in vitro</em>: Formation of β-Crystallin.

Upon addition of lens polyribosomes to a reticulocyte-cell-free system, α, β_L, and γ crystallin are synthesized, while β_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 βH crystallin formation depends upon the presence of a polypeptide βB_1b which arises by posttranslational modification. The putative precursor for βB_1b is a polypeptide βB_1a of which the messenger with a sedimentation coefficient of 12.5 S has been isolated. [ABSTRACT FROM AUTHOR]