title: Characterization of the spasmin 1 gene in Zoothamnium arbuscula strain Kawagoe (protozoa, ciliophora) and its relation to other spasmins and centrins.
abstract: Zoothamnium arbuscula strain Kawagoe is a giant sessile peritrich ciliated protozoa that possesses a contractile organelle called a spasmoneme. We report here on the molecular characterization and provide an opportunity to discuss the evolutionary relationships of the Z. arbuscula spasmin; spasmins belong to the calmodulin superfamily and are the major components of spasmoneme filaments. We analysed and obtained the whole sequence of the spasmin 1 gene and a partial sequence of the spasmin 2 gene. It is surprising that the sequence of spasmin 1 does not contain introns and encodes an open reading frame of 531 bp. It predicts a product of 177 amino acids with a calculated molecular mass of 19659 Da and a pI of 4.68. The amino acid sequence has two putative calcium-binding domains. One of them is a functional domain, as defined by the EF-hand consensus. The varieties of spasmins were revealed by comparison with amino acid components and molecular relationships of spasmin 1 protein and other spasmins. A comparison of the amino acid sequence between the Z. arbuscula spasmin and known centrins indicates that spasmins have a one residue deletion in the EF-hand domain-2 and four residue insertions in domain-4, as does the Vorticella spasmin. However, there are large variations in the amino acid sequence at domain-4 within spasmin 1, spasmin 2 and the Vorticella spasmin.
authors.affiliation: Department of Physics, School of Science and Engineering, Waseda University, 169-8555, Tokyo, Japan. t.itabashi@ruri.waseda
authors.forename: Takeshi
authors.initials: T
authors.lastname: Itabashi
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Mikami
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Asai
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D002147:Calmodulin / Q000145:classification; D016384:Consensus Sequence; D019143:Evolution, Molecular; D017125:Genes, Protozoan; D008969:Molecular Sequence Data; D005810:Multigene Family; D016802:Oligohymenophorea / Q000235:genetics* / Q000648:ultrastructure; D015388:Organelles / Q000737:chemistry; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000737:chemistry / Q000145:classification
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D015800:Protozoan Proteins; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D002118:Calcium