MUROPEPTIDE RECYCLING PATHWAY & BETA LACTAMASE INDUCTION

通过多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。游离小鼠三肽进口的MppA渗透酶途径影响多药耐药，因此充分了解这些途径对健康具有重要意义。本研究的广泛和长期目标是表征鼠蛋白三肽循环途径和Mpp渗透酶，Mpp是一种新的鼠蛋白三肽特异性外质结合蛋白依赖的渗透酶途径。我们假设循环途径和Mpp渗透酶途径都具有监测功能，可以发出细胞壁状况变化的信号，从而使细胞能够对这些变化做出适当的反应。除了探索这些假设之外，本研究还将通过表征AmpG渗透酶和NagZ β - n -乙酰氨基葡萄糖苷酶，以及通过确定其特异性和MppA本身的特异性来扩展我们对循环途径的理解。目的1:a.确定AmpG渗透酶的底物特异性，这种渗透酶是小鼠循环和β -内酰胺酶诱导所必需的。b.确定是否需要NagZ β - n -乙酰氨基葡萄糖酶来形成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3：确定MppA对鼠蛋白三肽、L- ala - γ - d - glu -meso- dap和其他由MppA促进输入的三肽的结合特异性及其结合常数。目标4：确定MppA是否参与了进展报告中描述的几个观察结果强烈建议的信号传导。目的5：测定MppA的晶体结构。目的6：确定MppA和OppA向外周的输出是否需要groESL。

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.