Allostery, the mechanism for transmitting chemical signals between spatially separated protein domains, is of significant interest due to the myriad of drug discovery applications. However, very little is known about the effect of temperature on allosteric mechanisms that permit thermophilic human pathogens to remain active at their native elevated temperatures. Here, we study the enzyme imidazole glycerol phosphate synthase (IGPS) from the thermophile T. maritima, as a potential therapeutic target. The allosteric ligand PRFAR binds to the HisF subunit of IGPS, enhancing glutamine hydrolysis in the HisH subunit by 5000-fold over its basal catalytic level at room temperature. Elevating temperatures from 303 to 350 K drastically enhances milisecond dynamics in both apo and PRFAR-bound IGPS, however PRFAR is less activating at higher temperatures. Here, we use long timescale molecular dynamics simulations to model how temperature and ligand binding affect the signal transduction in IGPS. We examine the effect on the secondary structure, HisF-HisH connectivity, and on the allosteric pathways through eigenvector centrality analysis. We show that higher temperatures and PRFAR binding increase flexibility in IGPS, enabling conformational sampling of an active enzyme form, and that PRFAR-induced motions propagate through well-defined and conserved amino acid residues. The findings corroborate solution NMR measurements, including direct experimental evidence for inter-domain motion, the central role played by helix hα1, and the short-range nature of correlations responsible for the allosteric mechanism.

Temperature-modulated allostery in the IGPS enzyme of a thermophile

2019 Fall National Meeting

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