Different evolution rates within the lens-specific beta-crystallin gene family.
We have determined the sequence of a rat beta A3/A1-crystallin complementary DNA (cDNA) clone and the (partial) sequence of the human beta B3-crystallin gene. Calculation of the ratio of silent to nonsynonymous substitution between orthologous beta A3/A1-, beta B3-, and other beta- and gamma-crystallin sequences revealed that the region encoding the two globular domains of the beta A3/A1-crystallin sequence is the best conserved during evolution, much better than the corresponding region of the beta B1-, beta B3-, or the gamma-crystallin sequences, and even better (at least in the rodent/frog comparison) than the well-conserved alpha A-crystallin sequence. Remarkably, the rate of change of the beta A3/A1-crystallin coding sequence does not differ in the rodent and primate lineages, in contrast with previous findings concerning the evolution rates of the alpha A- or gamma-crystallin sequences in these two lineages. Comparison of the regions that encode the four motifs of the beta-crystallin between orthologous mammalian sequences showed that the extent of nonsynonymous substitution in each of these four homologous motif regions is the same. However, when the orthologous beta-crystallin genes of more distantly related species (mammals vs chicken or frog) are compared, the extent of non-synonymous substitution is higher in the regions encoding the external motifs I and III than in the regions encoding the internal motifs II and IV. This phenomenon is also observed when paralogous members of the beta/gamma-crystallin supergene family are compared.
Aarts
H J
HJ
Laboratory of Molecular Biology, University of Nijmegen, The Netherlands.
Jacobs
E H
EH
van Willigen
G
G
Lubsen
N H
NH
Schoenmakers
J G
JG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002417:Cattle; D003459:Crystallins / Q000235:genetics*; D004247:DNA / Q000235:genetics; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D051381:Rats
D003459:Crystallins; D004247:DNA