Shi X, Parthun M R, Jaehning J A
Department of Biochemistry, Biophysics and Genetics, University of Colorado Health Sciences Center, Denver 80220, USA.
Gene. 1995 Nov 20;165(2):199-202. doi: 10.1016/0378-1119(95)00577-s.
Two Saccharomyces cerevisiae proteins of 21 and 27 kDa co-purify with a novel enhancer of Gal4p DNA binding activity (Egdp) [Parthun et al., Mol. Cell. Biol. 12 (1992) 5683-5689]. Mutations in the EGD1 gene encoding the 21-kDa protein (Egd1p) have been shown to affect the kinetics and extent of the Gal4p-mediated, galactose-induced activation of the GAL genes. Egd1p is homologous to human BTF3b, recently identified as the beta subunit of the heterodimeric nascent-polypeptide-associated complex (NAC) involved in ensuring signal-sequence-specific protein sorting and translocation [Wiedmann et al., Nature 370 (1994) 434-440]. We have cloned and characterized EGD2 encoding the 27-kDa protein and found that Egd2p is strikingly similar to the alpha subunit of human NAC. Yeast, therefore, contains a complex composed of Egd1p and Egd2p very similar to the NAC complex described in human cells. Disruption of EGD2, alone or in combination with an EGD1 disruption, causes no obvious phenotypes. The lack of phenotype, the high levels of EGD1 and EGD2 expression, and the identification of multiple human genes encoding NAC subunits suggest that the yeast EGD genes may be members of multigene families with redundant function.
两种分子量分别为21 kDa和27 kDa的酿酒酵母蛋白与一种新型的Gal4p DNA结合活性增强子（Egdp）共同纯化[Parthun等人，《分子与细胞生物学》12（1992）5683 - 5689]。编码21 kDa蛋白（Egd1p）的EGD1基因突变已被证明会影响Gal4p介导的、半乳糖诱导的GAL基因激活的动力学和程度。Egd1p与人的BTF3b同源，最近被鉴定为异二聚体新生多肽相关复合物（NAC）的β亚基，该复合物参与确保信号序列特异性的蛋白质分选和转运[Wiedmann等人，《自然》370（1994）434 - 440]。我们已经克隆并鉴定了编码27 kDa蛋白的EGD2，发现Egd2p与人NAC的α亚基惊人地相似。因此，酵母中含有一种由Egd1p和Egd2p组成的复合物，与人类细胞中描述的NAC复合物非常相似。单独破坏EGD2或与EGD1破坏联合破坏，均未导致明显的表型。缺乏表型、EGD1和EGD2的高表达水平以及多个编码NAC亚基的人类基因的鉴定表明，酵母EGD基因可能是具有冗余功能的多基因家族的成员。
