title: The structural organization of the ascidian, Halocynthia roretzi, calmodulin genes. The vicissitude of introns during the evolution of calmodulin genes.
abstract: Two distinct calmodulin (CaM) genes are isolated from the ascidian, Halocynthia roretzi, (Hr-CaM A and Hr-CaM B) and those structures are determined. There are three nucleotide substitutions, producing two amino acid differences between Hr-CaM A and Hr-CaM B, and those are corresponding to two of the known eight variable residues among metazoan CaMs. Both Hr-CaM A and Hr-CaM B are constructed from six exons and five introns, and the positions of introns are identical. The positions of introns of Hr-CaMs are also identical with those of vertebrate CaMs, except third introns. The third introns of Hr-CaMs are inserted at 28bp upstream when compared with vertebrate CaMs. Thus, sliding of the third intron might have occurred in only the ascidian lineage prior to the gene duplication that also occurred only in that lineage. In addition, with the comparison of the intron positions, we attempt to investigate the vicissitude of introns during the evolution of metazoan CaMs.
authors: Biological Institute, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
authors: H J
authors: HJ
authors: Yuasa
authors: H
authors: H
authors: Yamamoto
authors: T
authors: T
authors: Takagi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics*; D003001:Cloning, Molecular; D019143:Evolution, Molecular; D007438:Introns / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics; D015183:Restriction Mapping; D016415:Sequence Alignment; D014561:Urochordata / Q000235:genetics*
chemical_list: D002147:Calmodulin; D020033:Protein Isoforms