MUROPEPTIDE RECYCLING PATHWAY & BETA LACTAMASE INDUCTION

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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.