The structural microtubule-associated proteins, MAP2, MAP4 and tau,play an important role in the intracellular organization of microtubules by binding to microtubule. Recently, we revealed that MAP4 also could bind to actin filaments as MAP2, and the main actin-binding site was the Cterminal part of the Pro-rich region in microtubule-binding domain. In this study, we examined behavior of these structural MAPs when both actin filaments and microtubules coexisted in a sample. The results showed

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... at MAP4 and MAP2 but not tau bound to actin filament retained microtubule binding abilities, and consequently induced actin filament-microtubule bundles. On the other hand, all MAPs bound to microtubules could not bind to actin filaments. 1P170 単離したラジアルスポークと微小管との結合 Binding of the Isolated Radial Spokes and Microtubules Hitoshi Sakakibara, Youské Shimizu, Hiroaki Kojima (Bio-ICT, NICT) Radial spokes of eukaryotic flagella are large protein complexes (~2 M), which connect 9 peripheral microtubules and the central-pair apparatus. Two or three radial spokes are aligned in a 96 nm structural period on the A subfiber of the peripheral microtubules. Using purified radial spokes of Chlamydomonas and microtubules of porcine brain tubulin, we examined the binding of the radial spokes and microtubules. When the sample of radial spokes was incubated with microtubules and followed by centrifugation, they were co-sedimented. By negative-stain electron microscopy, we observed that the structures of similar configurations to the radial spokes were attached to the microtubules. These suggest that the purified radial spoke contains microtubule binding subunits. 1P171 海洋性ビブリオ菌のべん毛本数抑制に関与する FlhG の ATPase 活性の役割 Role of ATPase activity of FlhG on the negative regulation of the flagellar number in Vibrio alginolyticus Hikaru Hirata, Akari Takashima, Hiroki Ono, Michio Homma, Seiji Kojima (Div.Bio.Sci., Grad.Sch.Sci., Univ.Nagoya) Marine bacteria Vibrio alginolyticus has a single polar flagellum whose the number is regulated positively by FlhF and negatively by FlhG. FlhG is a homolog of MinD, a cell division inhibitor of Escherichia coli, which has an ATPase motif. Mutational analysis revealed that the ATPase motif is necessary for proper function of FlhG. Here we overproduced and purified FlhG, and measured its ATPase activity. We found that FlhG actually hydrolyzed ATP, and mutation D171A enhanced its activity although the corresponding mutation in MinD abolished ATPase activation by MinE. We expect that ATPase activity is related to the function of FlhG and that FlhG behaves in different way from MinD. We will discuss a mechanism of regulating the number of flagella in the meeting. 1P172 細胞収縮コラーゲンゲル中における分子の拡散挙動 Biomolecular diffusion in contracted collagen gel caused by fibroblasts