8c0u
From Proteopedia
1,6-anhydro-n-actetylmuramic acid kinase (AnmK) in complex with their natural substrates and products
Structural highlights
FunctionANMK_PSEAE Catalyzes the specific phosphorylation of 1,6-anhydro-N-acetylmuramic acid (anhMurNAc) with the simultaneous cleavage of the 1,6-anhydro ring, generating MurNAc-6-P. Is required for the utilization of anhMurNAc either imported from the medium or derived from its own cell wall murein, and thus plays a role in cell wall recycling (By similarity). Publication Abstract from PubMedThe bacterial cell envelope is the structure with which the bacterium both engages with, and is protected from, its environment. Within this envelop is a conserved peptidoglycan polymer which confers shape and strength to the cell envelop. The enzymatic processes that build, remodel, and recycle the chemical components of this cross-linked polymer are preeminent targets of antibiotics, and exploratory targets for emerging antibiotic structures. We report a comprehensive kinetic and structural analysis for one such enzyme, the Pseudomonas aeruginosa anhydro-N-acetylmuramic acid (anhNAM) kinase (AnmK). AnmK is an important enzyme in the peptidoglycan-recycling pathway of this pathogen. It catalyzes the remarkable pairing of hydrolytic ring-opening of anhNAM with concomitant ATP-dependent phosphoryl transfer. AnmK follows a random-sequential kinetic mechanism with respect to its anhNAM and ATP substrates. Crystallographic analyses of four distinct structures (apo AnmK, AnmK:AMPPNP, AnmK:AMPPNP:anhNAM and AnmK:ATP:anhNAM) demonstrate that both substrates enter the active site independently in an ungated conformation of the substrate subsites, with protein loops acting as gates for anhNAM binding. Catalysis occurs within a closed conformational state for the enzyme. We observe this state crystallographically using ATP-mimetic molecules. A remarkable X-ray structure for dimeric AnmK sheds light on the pre-catalytic and post-catalytic ternary complexes, one in each subunit. Computational simulations in conjunction with the four high-resolution X-ray structures reveal the full catalytic cycle. We further report that a P. aeruginosa strain with disrupted anmK gene is more susceptible to the beta-lactam imipenem compared to the wild-type strain. These observations position AnmK for understanding the nexus among peptidoglycan recycling, susceptibility to antibiotics, and bacterial virulence. Catalytic process of anhydro-N-acetylmuramic acid kinase (AnmK) from Pseudomonas aeruginosa.,El-Araby AM, Jimenez-Faraco E, Feltzer R, Martin-Garcia JM, Karri BR, Ramachandran B, Kim C, Fisher JF, Hermoso JA, Mobashery S J Biol Chem. 2023 Sep 1:105198. doi: 10.1016/j.jbc.2023.105198. PMID:37660917[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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