Cold adaptation of microtubule assembly and dynamics. Structural interpretation of primary sequence changes present in the alpha- and beta-tubulins of Antarctic fishes.
Cold adaptation of microtubule assembly and dynamics. Structural interpretation of primary sequence changes present in the alpha- and beta-tubulins of Antarctic fishes.
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发表时间：
2000
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通讯作者：
H. Detrich;S. K. Parker;R. Williams;E. Nogales;K. Downing
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作者：
H. Detrich;S. K. Parker;R. Williams;E. Nogales;K. Downing
与恒温动物不同，南极鱼类的微管在非常低的温度（-1.8摄氏度）下组装。增强这些微管组装的适应性是微管蛋白二聚体固有的，并将其在0℃下聚合的临界浓度降低到约0.9 mg/ml （Williams， R. C., Jr., Correia， J. J., and DeVries， A. L. (1985) Biochemistry 24, 2790-2798）。在这里，我们证明了南极鱼类的纯脑小管形成的微管在低（5℃）和高（25℃）温度下都表现出缓慢的动力学；聚合物生长和缩短的速度以及这些状态之间相互转换的频率相对于在哺乳动物微管（37摄氏度）中观察到的情况要小。为了研究微管蛋白初级序列的变化对南极鱼类微管功能特性的影响，我们对黄腹岩鳕鱼（Notothenia coriiceps） 9个α -微管蛋白和4个β -微管蛋白的脑cdna进行了测序，并对冰鱼（Chionodraco rastrospinosus） 4个α -微管蛋白和2个β -微管蛋白的脑cdna进行了测序。这些鱼类的微管被发现含有小组独特或罕见的残基取代，这些取代可以映射到侧面，原丝间表面或α和β多肽的内部；鱼小管的纵向相互作用面没有改变。在一些单体的S7-H9原丝间“M”环中存在四种变化（α中的A278T和S287T； β中的S280G和A285S），预计会增加这些区域的柔韧性。α -链（M302L或M302F）特有的第五个横向取代可能增加原丝间相互作用的疏水性。两个疏水取代（H5螺旋上的α:S187A和S6片上的β:Y202F）可以使单体稳定在有利于聚合的构象上。我们提出，南极鱼类微管组合的冷适应部分是通过微管单体的侧表面和核心的进化重组发生的。
The microtubules of Antarctic fishes, unlike those of homeotherms, assemble at very low temperatures (-1.8 degrees C). The adaptations that enhance assembly of these microtubules are intrinsic to the tubulin dimer and reduce its critical concentration for polymerization at 0 degrees C to approximately 0.9 mg/ml (Williams, R. C., Jr., Correia, J. J., and DeVries, A. L. (1985) Biochemistry 24, 2790-2798). Here we demonstrate that microtubules formed by pure brain tubulins of Antarctic fishes exhibit slow dynamics at both low (5 degrees C) and high (25 degrees C) temperatures; the rates of polymer growth and shortening and the frequencies of interconversion between these states are small relative to those observed for mammalian microtubules (37 degrees C). To investigate the contribution of tubulin primary sequence variation to the functional properties of the microtubules of Antarctic fishes, we have sequenced brain cDNAs that encode 9 alpha-tubulins and 4 beta-tubulins from the yellowbelly rockcod Notothenia coriiceps and 4 alpha-tubulins and 2 beta-tubulins from the ocellated icefish Chionodraco rastrospinosus. The tubulins of these fishes were found to contain small sets of unique or rare residue substitutions that mapped to the lateral, interprotofilament surfaces or to the interiors of the alpha- and beta-polypeptides; longitudinal interaction surfaces are not altered in the fish tubulins. Four changes (A278T and S287T in alpha; S280G and A285S in beta) were present in the S7-H9 interprotofilament "M" loops of some monomers and would be expected to increase the flexibility of these regions. A fifth lateral substitution specific to the alpha-chain (M302L or M302F) may increase the hydrophobicity of the interprotofilament interaction. Two hydrophobic substitutions (alpha:S187A in helix H5 and beta:Y202F in sheet S6) may act to stabilize the monomers in conformations favorable to polymerization. We propose that cold adaptation of microtubule assembly in Antarctic fishes has occurred in part by evolutionary restructuring of the lateral surfaces and the cores of the tubulin monomers.