Crystal structure of ATP phosphoribosyltransferase from Mycobacterium tuberculosis |
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Authors: | Cho Yoonsang Sharma Vivek Sacchettini James C |
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Affiliation: | Department of Biochemistry and Biophysics, Texas A & M University, College Station 77843-2128, USA. |
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Abstract: | The N-1-(5'-phosphoribosyl)-ATP transferase catalyzes the first step of the histidine biosynthetic pathway and is regulated by a feedback mechanism by the product histidine. The crystal structures of the N-1-(5'-phosphoribosyl)-ATP transferase from Mycobacterium tuberculosis in complex with inhibitor histidine and AMP has been determined to 1.8 A resolution and without ligands to 2.7 A resolution. The active enzyme exists primarily as a dimer, and the histidine-inhibited form is a hexamer. The structure represents a new fold for a phosphoribosyltransferase, consisting of three continuous domains. The inhibitor AMP binds in the active site cavity formed between the two catalytic domains. A model for the mechanism of allosteric inhibition has been derived from conformational differences between the AMP:His-bound and apo structures. |
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