In vitro synthesis of the major lens membrane protein.

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Abstract
The biosynthetic activity of a polyribosomal fraction isolated from the calf lens fiber plasma membrane-cytoskeleton complex by DNase I treatment was assayed. After translation of these polyribosomes in a reticulocyte cell-free system and analysis of the products by electrophoresis in sodium dodecyl sulfate gels, the preferential synthesis of a protein with an apparent MW of 26,000 was observed. With immunochemical characterization this protein, which apparently is not synthesized by free polyribosomes, is identical to the major intrinsic plasma membrane protein MP26 of lens fibers. Upon storage, the MW of the newly synthesized protein decreases to about 22,000. This phenomenon was previously observed for MP26 in isolated plasma membranes and may be due to the presence of a specific proteolytic cleaving site in the protein.