title: Molecular evolution of the Ca(2+)-binding photoproteins of the Hydrozoa.
abstract: Alignment of the primary structures of the hydrozoan photoproteins, aequorin, mitrocomin, clytin and obelin showed very strong amino acid sequence identities. The Ca(2+)-binding sites of the proteins were found to be highly conserved. The Ca(2+)-binding sites were also homologous to the Ca(2+)-binding sites of other Ca(2+)-binding proteins. However, aequorin, mitrocomin, clytin and obelin differed from other Ca(2+)-binding proteins in that they contained a relatively large number of cysteine, tryptophan, histidine, proline and tyrosine residues, suggesting that these residues may have evolved as part of the light-emitting mechanism. Construction of a phylogenetic tree showed that aequorin, mitrocomin, clytin and obelin form a closely related group of proteins.
mesh_terms: D000331:Aequorin / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D005075:Biological Evolution; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016208:Databases, Factual; D008164:Luminescent Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011161:Porifera / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D002135:Calcium-Binding Proteins; D008164:Luminescent Proteins; C083952:mitrocomin protein, Mitrocoma celluria; C010497:obelin; C046165:phialidin; D000331:Aequorin; D002118:Calcium