| Research Abstract |
A microtubule-associated protein, MAP200, was purified from miniprotoplasts of tobacco BY-2 cells and characterized. As a result; 1, the MAP200 is identical with the TMBP200 which was purified from tobacco BY-2 cells and characterized by Yasuhara et at.; 2, MAT200 did not bundle microtubules differently from the TMBP200; 3, the MAP200 accelrates tubulin polymerization; 4, The MAP200 forms a complex with tubulin; 5, the MAP200 predominantly exists in the cytoplasm and partly does on microtubules. These results lead us to have a hypothesis that a complex consted of the MAP200 and tubulin exists in the cytoplasm and accelrated microtubule elongation by shuttling mechanism. On the other hand. I and Dr.Hussey were collaborated and elucidated some propertied of MAP65; 1, Ala420 is important for its MT binding;2,pleiade4, a mutant in mitosis, has amino acid substitution for Ala420;3, the MAP65 forms a homodimer and the n-terminal region is important for this. In addition, we examined the participation of protein phosphorylation in bundling of cortical MTs and we found that DMAP disorganized cortical MTs in vivo and isolated cortical MTs were dispersed on treatment with phosphatase. These results strongly suggest that bundling of cortical MTs is regulated by phosphorylation of the MAP65.
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