[Planar charged clusters--structural invariants of the gamma-crystallin family of the crystalline lens: functional role and evolutionary conservatism].

Plane charge clusters from the calf eye lens protein gamma-crystallin are considered. The clusters consist of four to six side chain charged groups with interatomic distances in ionic pairs from 4 to 7 A. The charge clusters appear to decrease the hydrophilic potential of the molecular surface which maintains the transparent refracting lens medium of vertebrates with a very high protein concentration. It is shown that the charge pattern for different gene products of one species is conservative as well as for whole set of 25 sequences of vertebrates, including carp, frog, mouse, rat, calf and human. Taking into account "neutral mutations", Asp-Glu and Arg-Lys the homology of those charge positions is equal to 95-100%. Functionally important charge clusters are absent in the ancient structural motifs of gamma-crystallin.