title: p85 binds to G-actin in a Ca(2+)/calmodulin-dependent manner, thus regulating the initiation of cytokinesis in tetrahymena.
abstract: Tetrahymena p85 is localized to the presumptive division plane before the formation of contractile ring microfilaments. p85 binds to calmodulin in a Ca(2+)-dependent manner and both proteins colocalize to the division furrow. Inhibition of the binding of p85 and Ca(2+)/calmodulin prevents both the localization of p85 and calmodulin to the division plane and the formation of the contractile ring, suggesting that the interaction of p85 and Ca(2+)/calmodulin is important in the formation of the contractile ring. We investigated the mechanisms of the formation of contractile ring, and the relationship among p85, CaM, and actin using co-sedimentation assay: p85 binds to G-actin in a Ca(2+)/calmodulin-dependent manner, but does not bind to F-actin. Therefore, we propose that a Ca(2+)/calmodulin signal and its target protein p85 are cooperatively involved in the recruitment of G-actin to the division plane and the formation of the contractile ring.
authors.affiliation: Institute of Biological Sciences, University of Tsukuba, Ibaraki, Tsukuba, 305-8572, Japan.
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Gonda
authors.forename: Osamu
authors.initials: O
authors.lastname: Numata
mesh_terms: D008841:Actin Cytoskeleton; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D011485:Protein Binding / Q000502:physiology; D015800:Protozoan Proteins; D015398:Signal Transduction / Q000502:physiology; D013768:Tetrahymena / Q000166:cytology / Q000378:metabolism*
chemical_list: D000199:Actins; D002147:Calmodulin; D018797:Cell Cycle Proteins; D015800:Protozoan Proteins; C404904:p85 protein, Tetrahymena; D002118:Calcium