title: Cofilin-induced cooperative conformational changes of actin subunits revealed using cofilin-actin fusion protein.
abstract: To investigate cooperative conformational changes of actin filaments induced by cofilin binding, we engineered a fusion protein made of Dictyostelium cofilin and actin. The filaments of the fusion protein were functionally similar to actin filaments bound with cofilin in that they did not bind rhodamine-phalloidin, had quenched fluorescence of pyrene attached to Cys374 and showed enhanced susceptibility of the DNase loop to cleavage by subtilisin. Quantitative analyses of copolymers made of different ratios of the fusion protein and control actin further demonstrated that the fusion protein affects the structure of multiple neighboring actin subunits in copolymers. Based on these and other recent related studies, we propose a mechanism by which conformational changes induced by cofilin binding is propagated unidirectionally to the pointed ends of the filaments, and cofilin clusters grow unidirectionally to the pointed ends following this path. Interestingly, the fusion protein was unable to copolymerize with control actin at pH 6.5 and low ionic strength, suggesting that the structural difference between the actin moiety in the fusion protein and control actin is pH-sensitive.
authors: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan.|Cellular Informatics Lab., RIKEN, Wako, Saitama 351-0198, Japan.
authors: Nobuhisa
authors: N
authors: Umeki
authors: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan.|Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan.
authors: Keiko
authors: K
authors: Hirose
authors: Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan.|Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan.
authors: Taro Q P
authors: TQ
authors: Uyeda
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000378:metabolism*; D051339:Actin Depolymerizing Factors / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D004023:Dictyostelium / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins
chemical_list: D051339:Actin Depolymerizing Factors; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins