Beta-tubulin isotypes purified from bovine brain have different relative stabilities.
Beta-tubulin isotypes purified from bovine brain have different relative stabilities.
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从牛脑中纯化的β-微管蛋白同种型具有不同的相对稳定性。
DOI：
10.1021/bi972763d
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发表时间：
1998
期刊：
影响因子：
2.9
通讯作者：
Ludueña,RF
中科院分区：
文献类型：
--
作者：
Schwarz,PM;Liggins,JR;Ludueña,RF
七种脊椎动物β-微管蛋白同种型的高度保守性和组织特异性提供了间接证据，证明同种型之间可能存在体内功能差异。来自牛脑β同种型研究的令人信服的证据表明，体外存在显着的构象和功能差异，并暗示这些差异可能与体内功能有关。分子稳定性是先前未研究的在评估功能意义方面具有潜在重要性的参数。我们检测了从牛脑中纯化的αβII和αβIII微管蛋白二聚体的相对稳定性。使用探针监测疏水区域和巯基的暴露以及秋水仙碱结合的丧失（已知所有这些都伴随着微管蛋白的时间依赖性功能丧失）表明，当同种型在 37°C 下孵育时，相对于 αβIII，αβII 中这些标准的加速。使用差示扫描量热法的研究表明，同种型在 ~60 °C 的展开和在 0 °C 的衰变都是高度协同的。还观察到αβIII在0℃孵育20小时后具有更高的熔化温度和更多保留三级结构的分子。这些研究支持以下结论：αβIII 明显比 αβII 更稳定，并提出了微管蛋白同种型相对稳定性的差异可能对调节体内微管功能特性很重要的可能性。
The highly conserved nature and tissue specificity of the seven vertebrate β-tubulin isotypes provide circumstantial evidence that functional differences among isotypes may exist in vivo. Compelling evidence from studies of bovine brain β-isotypes indicated significant conformational and functional differences in vitro and implied that these differences could be related to in vivo function. A previously uninvestigated parameter of potential importance in assessing functional significance is molecular stability. We examined the relative stability of αβIIand αβIIItubulin dimers purified from bovine brain. The use of probes to monitor the exposure of hydrophobic areas and sulfhydryls and the loss of colchicine binding, all of which are known to accompany tubulin's time-dependent loss of function, showed an acceleration of these criteria in αβIIrelative to αβIIIwhen the isotypes were incubated at 37 °C. Studies using differential scanning calorimetry suggested that unfolding of the isotypes at ∼60 °C and decay at 0 °C were both highly cooperative. It was also observed that αβIIIhad a higher melting temperature and a larger population of molecules retaining tertiary structure after incubation at 0 °C for 20 h. These studies support the conclusion that αβIIIis significantly more stable than αβIIand raise the possibility that differences in relative stabilities of tubulin isotypes may be important in regulating the functional properties of microtubules in vivo.