Wilson R L, Stauffer G V
Department of Microbiology, University of Iowa, Iowa City 52242.
J Bacteriol. 1994 May;176(10):2862-8. doi: 10.1128/jb.176.10.2862-2868.1994.
The gene encoding GcvA, the trans-acting regulatory protein for the Escherichia coli glycine cleavage enzyme system, has been sequenced. The gcvA locus contains an open reading frame of 930 nucleotides that could encode a protein with a molecular mass of 34.4 kDa, consistent with the results of minicell analysis indicating that GcvA is a polypeptide of approximately 33 kDa. The deduced amino acid sequence of GcvA revealed that this protein shares similarity with the LysR family of activator proteins. The transcription start site was found to be 72 bp upstream of the presumed translation start site. A chromosomal deletion of gcvA resulted in the inability of cells to activate the expression of a gcvT-lacZ gene fusion when grown in the presence of glycine and an inability to repress gcvT-lacZ expression when grown in the presence of inosine. The regulation of gcvA was examined by constructing a gcvA-lacZ gene fusion in which beta-galactosidase synthesis is under the control of the gcvA regulatory region. Although gcvA expression appears to be autogenously regulated over a two- to threefold range, it is neither induced by glycine nor repressed by inosine.
编码大肠杆菌甘氨酸裂解酶系统反式作用调节蛋白GcvA的基因已被测序。gcvA基因座包含一个930个核苷酸的开放阅读框，可编码一个分子量为34.4 kDa的蛋白质，这与小细胞分析结果一致，表明GcvA是一种分子量约为33 kDa的多肽。GcvA推导的氨基酸序列显示，该蛋白与激活蛋白的LysR家族具有相似性。发现转录起始位点在假定翻译起始位点上游72 bp处。gcvA的染色体缺失导致细胞在甘氨酸存在下生长时无法激活gcvT - lacZ基因融合的表达，在肌苷存在下生长时无法抑制gcvT - lacZ的表达。通过构建一个β-半乳糖苷酶合成受gcvA调控区域控制的gcvA - lacZ基因融合来研究gcvA的调控。尽管gcvA的表达似乎在两到三倍的范围内受到自身调节，但它既不被甘氨酸诱导，也不被肌苷抑制。
