beta s-Crystallin: structure and evolution of a distinct member of the beta gamma-superfamily.
The nucleotide sequence of the cDNA of bovine lens beta s-crystallin has been determined, and the derived amino acid sequence has been confirmed by amino acid compositions and partial sequences of the tryptic peptides of this monomeric protein. beta s-Crystallin has a length of 177 residues, corresponding to a mol. wt. of 20 773, and a blocked N-terminal serine. Comparison of beta s with the known sequences of other beta- and gamma-crystallins, and computer construction of a phylogenetic tree of these sequences, shows beta s to be more closely related to the monomeric gamma-crystallins than to the oligomeric beta-crystallins. Also the tertiary structure of beta s modelled by interactive computer graphics on the coordinates of gamma II-crystallin, revealed similarities with the gamma-crystallins which might explain its monomeric behavior: the presence of a very short N-terminal 'arm' as compared with the beta-crystallins; a distribution of charged residues on the surface as in the gamma-crystallins; and finally the nature of certain residues of its inter-domain contacts. beta s-Crystallin seems to be an old and isolated offshoot of the gamma-family, and, considering its ancient origin, might well be present in other, non-mammalian, vertebrate classes.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002417:Cattle; D003001:Cloning, Molecular; D003459:Crystallins / Q000235:genetics*; D005796:Genes; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D003459:Crystallins; D012333:RNA, Messenger