Phosphatase-sensitive regulators of microtubule assembly copurify with sea urchin egg microtubules
Phosphatase-sensitive regulators of microtubule assembly copurify with sea urchin egg microtubules
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DOI：
10.1002/(sici)1097-010x(19990215)283:3
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发表时间：
1999-02-15
影响因子：
--
通讯作者：
Suprenant, KA
中科院分区：
文献类型：
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作者：
Brisch, E;Ahrens, DP;Suprenant, KA
The purpose of this study was to identify phosphoproteins that affect microtubule assembly in sea urchins. We examined protein targets of endogenous kinases and phosphatases in purified sea urchin egg microtubule protein (MTP). Seven polypeptides of Mr 105, 77, 55, 48, 44, 33, and 20 kD are phosphorylated in MTP purified in vitro. The 77 kD phosphoprotein is the major microtubule-associated protein (MAP) in sea urchins, and the 55 kD phosphoprotein is beta-tubulin. The remaining phosphoproteins are unidentified. To determine whether these phosphorylation events affected microtubule assembly, we utilized okadaic acid, an inhibitor of type 1 and 2A protein phosphatases, and 6-dimethylaminopurine (6-DMAP), a general protein kinase inhibitor. Treatment with 6-DMAP had little significant effect on the microtubule length distribution or the microtubule number concentration. In contrast, okadaic acid treatment resulted in a 29% overall shortening in microtubule length, a 35% increase in the microtubule number concentration, and a 16% decrease in cold-labile microtubule mass. The phosphorylation state of the 77 kD echinoderm MAP was unaffected by okadaic acid treatment. In contrast, the appearance of two small phosphoproteins correlated with the okadaic acid effects on microtubule length and number. We speculate that these proteins, Mr 44 and 48 kD, contribute to the regulation of microtubule assembly in sea urchin embryos. (C) 1999 Wiley-Liss, Inc.
