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CORRELATED CHANGES IN δ‐CRYSTALLIN SYNTHESIS AND ION CONCENTRATIONS IN THE EMBRYONIC CHICK LENS: SUMMARY, CURRENT EXPERIMENTS AND SPECULATIONS

We have described a correlation between the ratio of synthesis of the higher to the lower molecular weight polypeptides of δ‐crystallin and the intracellular concentrations of Na+ and K+ in the cultured embryonic chick lens. The only structural differences we have found between the larger and smaller δ‐crystallin polypeptides are two, acidic, methionine‐containing tryptic peptides which are absent from the lower molecular weight polypeptides. We do not yet know whether the alteration in the ratio of synthesis of the polypeptides is regulated at the post‐transcriptional or post‐translational level. We are continuing to investigate this problem by studies on the cell‐free synthesis of δ‐crystallin and by analysis of the sequences and organization of δ‐crystallin DNA.