title: Homologues of radial spoke head proteins interact with Ca2+/calmodulin in Tetrahymena cilia.
abstract: Calmodulin (CaM) is an axonemal component. To examine the pathway of Ca(2+)/CaM signaling in cilia, using Ca(2+)/CaM-affinity column, we identified seven Ca(2+)/CaM-associated proteins from a crude dynein fraction and isolated 62 kDa (p62) and 66 kDa (p66) Ca(2+)/CaM-associated proteins in Tetrahymena cilia. The amino acid sequences deduced from the p62 and p66 cDNA sequences suggested that these proteins were similar to Chlamydomonas radial spoke proteins 4 and 6 (RSP4 and RSP6), components of the radial spoke head, and sea urchin sperm p63, which is a homologue of RSP4/6, and isolated as a key component that affect flagellar bending patterns. Although p62 and p66 do not have a conventional CaM-binding site, those have consecutive sequences which showed high normalized scores (>or= 5) from a CaM target database. These consecutive sequences were also found in RSP4, RSP6, and p63. These radial spoke heads proteins have a high similarity region composed of 15 amino acids between the five proteins. Immunoelectron microscopy using anti-CaM antibody showed that CaM was localized along the outer edge of the curved central pair microtubules in axoneme. Therefore, it is possible that the interaction between Ca(2+)/CaM and radial spoke head control axonemal curvature in the ciliary and flagellar waveform.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572.
authors.forename: Hironori
authors.initials: H
authors.lastname: Ueno
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Iwataki
authors.forename: Osamu
authors.initials: O
authors.lastname: Numata
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism / Q000648:ultrastructure; D004398:Dyneins / Q000378:metabolism; D008297:Male; D046529:Microscopy, Electron, Transmission; D008870:Microtubules / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013768:Tetrahymena / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002147:Calmodulin; D010940:Plant Proteins; D015800:Protozoan Proteins; C060324:radial spoke protein, Chlamydomonas; D004398:Dyneins; D002118:Calcium