Campylobacter jejuni adenosine triphosphate phosphoribosyltransferase is an active hexamer that is allosterically controlled by the twisting of a regulatory tail |
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| Authors: | Gerd Mittelstädt Gert‐Jan Moggré Santosh Panjikar Ali Reza Nazmi Emily J. Parker |
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| Affiliation: | 1. Maurice Wilkins Centre, Biomolecular Interaction Centre, Christchurch, New Zealand;2. Department of Chemistry, University of Canterbury, Christchurch, New Zealand;3. Australian Synchrotron, Clayton, Melbourne, Victoria, Australia;4. Department of Biochemistry and Molecular Biology, Monash University, Clayton, Campus, Melbourne, Victoria, Australia;5. Biomolecular Interaction Centre and School of Biological Sciences, University of Canterbury, Christchurch, New Zealand |
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| Abstract: | Adenosine triphosphate phosphoribosyltransferase (ATP‐PRT) catalyzes the first committed step of the histidine biosynthesis in plants and microorganisms. Here, we present the functional and structural characterization of the ATP‐PRT from the pathogenic ε‐proteobacteria Campylobacter jejuni (CjeATP‐PRT). This enzyme is a member of the long form (HisGL) ATP‐PRT and is allosterically inhibited by histidine, which binds to a remote regulatory domain, and competitively inhibited by AMP. In the crystalline form, CjeATP‐PRT was found to adopt two distinctly different hexameric conformations, with an open homohexameric structure observed in the presence of substrate ATP, and a more compact closed form present when inhibitor histidine is bound. CjeATP‐PRT was observed to adopt only a hexameric quaternary structure in solution, contradicting previous hypotheses favoring an allosteric mechanism driven by an oligomer equilibrium. Instead, this study supports the conclusion that the ATP‐PRT long form hexamer is the active species; the tightening of this structure in response to remote histidine binding results in an inhibited enzyme. |
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| Keywords: | ATP‐PRT phosphoribosyltransferase HisG allostery conformational change |
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