Rivero F, Dislich H, Glöckner G, Noegel A A
Institut für Biochemie I, Medizinische Fakultät, Universität zu Köln, Joseph-Stelzmann-Strasse 52, D-50931 Köln, Germany.
Nucleic Acids Res. 2001 Mar 1;29(5):1068-79. doi: 10.1093/nar/29.5.1068.
Taking advantage of the ongoing Dictyostelium genome sequencing project, we have assembled >73 kb of genomic DNA in 15 contigs harbouring 15 genes and one pseudogene of Rho-related proteins. Comparison with EST sequences revealed that every gene is interrupted by at least one and up to four introns. For racC extensive alternative splicing was identified. Northern blot analysis showed that mRNAs for racA, racE, racG, racH and racI were present at all stages of development, whereas racJ and racL were expressed only at late stages. Amino acid sequences have been analysed in the context of Rho-related proteins of other organisms. Rac1a/1b/1c, RacF1/F2 and to a lesser extent RacB and the GTPase domain of RacA can be grouped in the Rac subfamily. None of the additional Dictyostelium Rho-related proteins belongs to any of the well-defined subfamilies, like Rac, Cdc42 or Rho. RacD and RacA are unique in that they lack the prenylation motif characteristic of Rho proteins. RacD possesses a 50 residue C-terminal extension and RacA a 400 residue C-terminal extension that contains a proline-rich region, two BTB domains and a novel C-terminal domain. We have also identified homologues for RacA in Drosophila and mammals, thus defining a new subfamily of Rho proteins, RhoBTB.
利用正在进行的盘基网柄菌基因组测序项目，我们在15个重叠群中组装了超过73 kb的基因组DNA，这些重叠群包含15个基因和1个Rho相关蛋白的假基因。与EST序列比较发现，每个基因至少被1个内含子打断，最多被4个内含子打断。对于racC，鉴定出了广泛的可变剪接。Northern印迹分析表明，racA、racE、racG、racH和racI的mRNA在发育的各个阶段都存在，而racJ和racL仅在后期表达。已在其他生物体的Rho相关蛋白背景下分析了氨基酸序列。Rac1a/1b/1c、RacF1/F2以及程度稍低的RacB和RacA的GTPase结构域可归为Rac亚家族。盘基网柄菌其他Rho相关蛋白均不属于任何已明确的亚家族，如Rac、Cdc42或Rho。RacD和RacA的独特之处在于它们缺乏Rho蛋白特有的异戊二烯化基序。RacD具有一个50个残基的C末端延伸，RacA具有一个400个残基的C末端延伸，其中包含一个富含脯氨酸的区域、两个BTB结构域和一个新的C末端结构域。我们还在果蝇和哺乳动物中鉴定出了RacA的同源物，从而定义了一个新的Rho蛋白亚家族，即RhoBTB。
