Human lens gamma-crystallins: isolation, identification, and characterization of the expressed gene products.
We have isolated the individual gamma-crystallins expressed in young human lenses and identified with which of the six known human gamma-crystallin genes they each correspond. We find that at least 90% of the gamma-crystallins synthesized in the young human lens are the products of genes gamma G3 and gamma G4. We demonstrate that gamma G4-crystallin undergoes a temperature-dependent phase separation, and we have measured the low-concentration branch of its coexistence curve (phase separation temperature vs. concentration) up to about 40 mg/ml. By comparison, we found no evidence of gamma G3-crystallin phase separating, even at lower temperatures and higher concentrations. This is consistent with predictions based on sequence homology between human and rat gamma-crystallins. The implications of these findings for human inherited and senile cataracts are considered.
D000375:Aging / Q000378:metabolism; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002386:Cataract / Q000209:etiology; D002417:Cattle; D002675:Child, Preschool; D003459:Crystallins / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D005810:Multigene Family; D051381:Rats
D000596:Amino Acids; D003459:Crystallins