MUROPEPTIDE RECYCLING PATHWAY & BETA LACTAMASE INDUCTION

通过肌肽循环途径摄取细胞壁降解产物是诱导β-内酰胺酶所必需的。MPPA通透酶途径影响着多药耐药，因此对这些途径的全面了解对健康具有重要意义。本研究的长期目标是研究肌动蛋白三肽循环途径和MPP通透酶，这是一种新的针对肌动蛋白三肽的周质结合蛋白依赖的通透酶途径。我们假设，循环途径和MPP渗透酶途径都具有监测细胞壁条件变化的信号功能，从而使细胞能够对这些变化做出适当的反应。除了探索这些假说外，这项拟议的研究还将通过确定AMPG渗透酶和NagZβ-N-乙酰氨基葡萄糖苷酶的特性来扩展我们对循环途径的理解，并通过确定MPPA的特异性和MPPA本身的特性来表征MPPA渗透酶途径。具体目的：目的1：确定AMPG渗透酶的底物专一性，AMPG渗透酶是毛霉素素循环和β-内酰胺酶诱导所必需的。B.确定是否需要NagZβ-N-乙酰氨基葡萄糖苷酶来形成β-内酰胺酶的诱导剂，并确定NagZ的底物特异性。目的2：确定循环途径是否参与向细胞发出细胞壁受损的信号。目的：测定MPPA与麦尿苷三肽、L-丙氨酸-γ-D-谷氨酸-Meso-Dap等易于输入的三肽的结合特异性及其结合常数。目的4：确定MPPA是否参与信号传递，这是进度报告中描述的几个观察结果强烈表明的。目的5：确定MPPA的晶体结构。目的6：确定是否需要groESL才能将MPPA和OPPA输出到周质。

Uptake of cell wall degradation products via the muropeptide recycling pathway is required for induction of beta-lactamase. The MppA permease pathway for import of free murein tripeptide affects multidrug resistance so that a full understanding of these pathways has important implications for health. The broad, long-term objective of this research is to characterize the murein tripeptide recycling pathway and the Mpp permease, a new periplasmic binding-protein dependent permease pathway specific for murein tripeptide. We hypothesize that both the recycling pathway and the Mpp permease pathway have a monitoring function to signal changes in the condition of the cell wall so that the cell can respond to the changes appropriately. In addition to exploring these hypotheses, the proposed research will extend our understanding of the recycling pathway by characterizing the AmpG permease and the NagZ beta-N-acetylglucosaminidase and of the MppA permease pathway by determining its specificity and that of MppA itself. Specific aims: Aim 1: a. To determine the substrate specificity of AmpG permease, a permease required for murein recycling and beta-lactamase induction. b. To determine if NagZ beta-N-acetylglucosaminidase is needed to form the inducer for beta-lactamase and to determine the substrate specificity of NagZ. Aim 2: To determine if the recycling pathway is involved in signaling to the cell that its cell wall is being damaged. Aim 3: To determine the binding specificity of MppA and its binding constants for the murein tripeptide, L- Ala-gamma-D-Glu-meso-Dap and other tripeptides whose importation is facilitated by MppA. Aim 4: To determine if MppA is involved in signaling which is strongly suggested by several observations described in the progress report. Aim 5: To determine the crystal structure of MppA. Aim 6: To determine if groESL is required for export of MppA and OppA to the periplasm.