Tuma P L, Stachniak M C, Collins C A
Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, Chicago, Illinois 60611.
J Biol Chem. 1993 Aug 15;268(23):17240-6.
Dynamin is a GTPase thought to play a role in endocytosis based on genetic analysis of its homolog in Drosophila melanogaster shibire. Previous studies have stressed an in vitro association with microtubules, though additional evidence suggests that dynamin associates with membranous organelles. In an analysis of the enzymatic and membrane binding properties of dynamin, we have found that the acidic phospholipids, phosphatidylserine, phosphatidylglycerol, and phosphatidylinositol, are able to stimulate GTP hydrolysis in a manner similar to activation previously shown with microtubules. A neutral phospholipid, phosphatidylcholine, had no effect on dynamin GTPase. Activation of dynamin was biphasic, with a decrease in activity back to basal levels with increased concentrations of either microtubules or liposomes. A comparison between GTPase stimulation induced by microtubules and that by phospholipids suggests that ionic interactions between the basic C-terminal domain of dynamin and the negatively charged microtubule or phospholipid head group are important. In support of this, GTPase stimulation by these agents in combination was not additive. A salt-extracted membrane fraction from brain tissue also activated dynamin GTPase, though to a lower extent than pure phospholipids. These results suggest that membrane components could be responsible for some aspects of the regulation of dynamin function in vivo.
发动蛋白是一种GTP酶，基于对其在黑腹果蝇“麻痹”突变体中同源物的遗传分析，人们认为它在胞吞作用中发挥作用。以往的研究强调了它在体外与微管的结合，不过更多证据表明发动蛋白与膜性细胞器有关。在对发动蛋白的酶活性和膜结合特性的分析中，我们发现酸性磷脂，即磷脂酰丝氨酸、磷脂酰甘油和磷脂酰肌醇，能够以一种类似于先前微管激活的方式刺激GTP水解。中性磷脂磷脂酰胆碱对发动蛋白GTP酶没有影响。发动蛋白的激活是双相的，随着微管或脂质体浓度的增加，活性会下降回到基础水平。微管诱导的GTP酶刺激与磷脂诱导的刺激之间的比较表明，发动蛋白碱性C末端结构域与带负电荷的微管或磷脂头部基团之间的离子相互作用很重要。支持这一点的是，这些试剂联合诱导的GTP酶刺激不是相加的。脑组织盐提取的膜组分也能激活发动蛋白GTP酶，不过程度低于纯磷脂。这些结果表明，膜成分可能在体内发动蛋白功能调节的某些方面起作用。
