Burbelo P D, Drechsel D, Hall A
Medical Research Council Laboratory for Molecular Cell Biology, University College London, United Kingdom.
J Biol Chem. 1995 Dec 8;270(49):29071-4. doi: 10.1074/jbc.270.49.29071.
Rho, Rac, and Cdc42 are small GTPases that regulate the formation of a variety of actin structures and the assembly of associated integrin complexes, but little is known about the target proteins that mediate their effects. Here we have used a motif-based search method to identify putative effector proteins for Rac and Cdc42. A search of the GenBankTM data base for similarity with the minimum Cdc42/Rac interactive binding (CRIB) region of a potential effector protein p65PAK has identified over 25 proteins containing a similar motif from a range of different species. These candidate Cdc42/Rac-binding proteins include family members of the mixed lineage kinases (MLK), a novel tyrosine kinase from Drosophila melanogaster (DPR2), a human protein MSE55, and several novel yeast and Caenorhabditis elegans proteins. Two murine p65PAK isoforms and a candidate protein from C. elegans, F09F7.5, interact strongly with the GTP form of both Cdc42 and Rac, but not Rho in a filter binding assay. Three additional candidate proteins, DPR2, MSE55, and MLK3 showed binding to the GTP form of Cdc42 and weaker binding with Rac, and again no interaction with Rho. These results indicate that proteins containing the CRIB motif bind to Cdc42 and/or Rac in a GTP-dependent manner, and they may, therefore, participate in downstream signaling.
Rho、Rac和Cdc42是小GTP酶，它们调节多种肌动蛋白结构的形成以及相关整合素复合物的组装，但对于介导其作用的靶蛋白却知之甚少。在此，我们使用了基于基序的搜索方法来鉴定Rac和Cdc42的假定效应蛋白。通过在GenBankTM数据库中搜索与潜在效应蛋白p65PAK的最小Cdc42/Rac相互作用结合（CRIB）区域相似的序列，已从一系列不同物种中鉴定出25种以上含有相似基序的蛋白。这些候选的Cdc42/Rac结合蛋白包括混合谱系激酶（MLK）家族成员、一种来自黑腹果蝇的新型酪氨酸激酶（DPR2）、一种人类蛋白MSE55以及几种新型酵母和秀丽隐杆线虫蛋白。在滤膜结合试验中，两种小鼠p65PAK异构体和一种来自秀丽隐杆线虫的候选蛋白F09F7.5与Cdc42和Rac的GTP形式强烈相互作用，但与Rho无相互作用。另外三种候选蛋白DPR2、MSE55和MLK3显示出与Cdc42的GTP形式结合，与Rac的结合较弱，同样与Rho无相互作用。这些结果表明，含有CRIB基序的蛋白以GTP依赖的方式与Cdc42和/或Rac结合，因此它们可能参与下游信号传导。
