Kopp U, Wiedemann B, Lindquist S, Normark S
Institut für Medizinische Mikrobiologie und Immunologie, University of Bonn, Germany.
Antimicrob Agents Chemother. 1993 Feb;37(2):224-8. doi: 10.1128/AAC.37.2.224.
The ampD gene product regulates the expression of AmpC beta-lactamase in gram-negative bacteria and is proposed to be involved in peptidoglycan metabolism. In this study, we sequenced the ampD wild type and three mutant genes of Enterobacter cloacae and Citrobacter freundii. They exhibited a high degree of homology with the corresponding gene of Escherichia coli except in the carboxy termini, where, in the wild-type genes of E. cloacae and C. freundii, four additional amino acids yielding the Ser-X-X-Lys motif were found. Evidence that this C-terminal region of the ampD gene product is necessary for activity was shown by constructing a deletion of the last 16 amino acids. The spontaneous mutation of ampD02 is an out-of-frame insertion and yields an inactive AmpD protein. The single-base-pair substitution of Gly for Asp-121 in ampD05 is responsible for a hyperinducible phenotype. These results demonstrate regions of the ampD gene and the corresponding protein which have functional importance for the induction of AmpC beta-lactamase in E. cloacae.
ampD基因产物可调节革兰氏阴性菌中AmpCβ-内酰胺酶的表达，并被认为参与肽聚糖代谢。在本研究中，我们对阴沟肠杆菌和弗氏柠檬酸杆菌的ampD野生型基因及三个突变基因进行了测序。除了羧基末端外，它们与大肠杆菌的相应基因具有高度同源性，在阴沟肠杆菌和弗氏柠檬酸杆菌的野生型基因的羧基末端，发现了另外四个产生Ser-X-X-Lys基序的氨基酸。通过构建缺失最后16个氨基酸的片段，证明了ampD基因产物的这个C末端区域对活性是必需的。ampD02的自发突变是一个移码插入，产生无活性的AmpD蛋白。ampD05中Asp-121被Gly的单碱基对取代导致了超诱导表型。这些结果证明了ampD基因及相应蛋白质的区域对阴沟肠杆菌中AmpCβ-内酰胺酶的诱导具有功能重要性。
