Stenotrophomonas maltophilia 之 AmpH 蛋白以 Dose-Dependent 方式調控L1 及 L2 β-lactamases 之表現; AmpH Regulates the Expression of the Chromosomal L1 and L2 β-lactamases of Stenotrophomonas maltophilia in a Does-Dependent Manner

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Title:	Stenotrophomonas maltophilia 之 AmpH 蛋白以 Dose-Dependent 方式調控L1 及 L2 β-lactamases 之表現;AmpH Regulates the Expression of the Chromosomal L1 and L2 β-lactamases of Stenotrophomonas maltophilia in a Does-Dependent Manner
Authors:	黃紹晟;Shao-Cheng Huang
Contributors:	中國醫藥大學：醫學檢驗生物技術學系碩士班
Keywords:	操縱組;嗜麥芽糖黃單胞菌;Stenotrophomonas maltophilia;AmpH;L2 beta-lactamases;operon
Date:	2009-07-07
Issue Date:	2009-08-12 17:09:55 (UTC+8)
Abstract:	Stenotrophomonas maltophilia 有一誘發型的L2 β-lactamase，其誘發表現通常會被位於上游的 ampR 基因所調控。本論文中，利用即時定量 PCR(QRT-PCR)、反轉錄酶 PCR(RT-PCR)、實驗去證實 L2 基因及其下游 ampH 基因型成一 operon。而 ampH 基因的表現依靠 ampR 基因調控的啟動子(PL2) 及其自己的啟動子(PampH) 。在菌株 S. maltophilia的基因體序列中， ampH 基因被命名為 putative Na+/H+ antipoter ；卻發現其功能對於維持鈉鹽類的平衡關係似乎不大，反而是調控 L1 和 L2 β-lactamases 基因的誘發表現。而 AmpH 蛋白對於調控L1 和 L2 基因的誘發表現與劑量有關；當 AmpH 蛋白表現量不足會使 L1 基因的誘發表現量下降，但 AmpH 蛋白表現量太多也會使 L2 基因的誘發表現量下降。因此，細菌菌株為了達到 L1 及 L2 β-lactamases 蛋白的最佳誘發量，很巧妙地以 L2-ampH operon 的型式組裝，使得AmpH蛋白在PL2 啟動子的誘發下足量表現，此可增加 L1 β-lactamase 的誘發量卻又不因過多的 AmpH 蛋白被誘發產生，而折損 L2 β-lactamase 蛋白的誘發量。所以，以 L2-ampH operon down-regulation 調控的模式，控制 AmpH 蛋白的誘發量足以增加 L1 β-lactamase 的誘發量但不會減少 L2 β-lactamase 的誘發量。 The L2 β-lactamase gene of Stenotrophomonas maltophilia has been shown to be involved in resistance of the β-lactams and its expression is regulated by the ampR gene, which divergently locates upstream of the L2 gene. In this study, L2 and its downstream gene, ampH, has been shown to be an operon as revealed by Quantitative Real-Time PCR (QRT-PCR), Reverse Transcriptase-PCR (RT-PCT), and chromosomal transcriptional fusion assay. The expression of ampH gene depends on the ampR-regulated L2 promoter (PL2) and its own promoter (PampH). The ampH gene previously annotated as a putative Na+/H+ antiporter in the genome project of S. maltophilia was found to be less involved in the sodium homeostasis, but more prominent in the regulation of the induction of L1 and L2 β-lactamase genes. The role of AmpH protein in the regulation of L1 and L2 genes induction is does-dependent. The induction of L1 gene in the absence of the AmpH protein proceeds to fewer extents, indicating the optimal L1 induction occurs with the support of sufficient AmpH. In contrast, the presence of surplus AmpH protein reduces the induction of L2 gene, while hardly influences the induction of L1 gene. Consequently, the optimal L1 and L2 induction is exquisitely controlled by an appropriate amount of AmpH protein, which may be cleverly administered by the down-regulated L2-ampH operon.
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