Incorporation in vitro of lens membrane protein into reticulocyte membranes.
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Biomedical subjects
Publications and source records attributed to J M Hilderink.
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In the calf eye lens, four morphologically distinct cell types can be detected: three in the epithelial monolayer and one in the cortical part. During differentiation, there is a quantitative change in the synthesis of crystallin subunits. A marked increase in alphaA-chains and several beta-crystallin polypeptides accompanies the transition from epithelial to fiberlike lens cells while synthesis of the non-crystallin proteins diminishes significantly.
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Lens epithelial cells can be kept in their original differentiated state or brought to dedifferentiation depending on the culture conditions. The different stages of differentiation can be identified using specific markers, namely the activity of steroid metabolizing enzymes, and the synthesis of specific structural lens polypeptides. For this reason lens epithelial cells in tissue culture provide a unique system for the study of the regulation of RNA and protein biosynthesis.
Affinith chromatography of lens polyribosomal RNA on oligo(dT)-cellulose yields three fractions. As arule the second fraction has been neglected in other studies reported in the literature. According to our investigations this fraction in particular contains the messengers for the non-crystallin lens proteins.
1. The lens cell-free system synthesizes in addition to the crystallins, polypeptides which co-electrophorese with lens plasma membrane protein components. 2. Isolated lens polysomes can be translated in a heterologous cell-free system. They code for both the crystallins and membrane-protein-like components. 3. If messengers isolated from these polysomes by affinity chromatography on oligo-(dT)-cellulose are added to a heterologous cell-free system, only lens proteins of lower molecular weight are synthesized. 4. Different ionic conditions are required for optimal translation of different lens messengers.