A dimeric catalytic core relates the short and long forms of ATP-phosphoribosyltransferase

Abstract

Adenosine triphosphate (ATP) phosphoribosyltransferase (ATP-PRT) catalyses the first committed step of histidine biosynthesis in plants and microorganisms. Two forms of ATP-PRT have been reported, which differ in their molecular architecture and mechanism of allosteric regulation. The short-form ATP-PRT is a hetero-octamer, with four HisG chains that comprise only the catalytic domains and four separate chains of HisZ required for allosteric regulation by histidine. The long-form ATP-PRT is homo-hexameric, with each chain comprising two catalytic domains and a covalently linked regulatory domain that binds histidine as an allosteric inhibitor. Here, we describe a truncated long-form ATP-PRT from devoid of its regulatory domain (ATP-PRT). Results showed that ATP-PRT is dimeric, exhibits attenuated catalytic activity, and is insensitive to histidine, indicating that the covalently linked regulatory domain plays a role in both catalysis and regulation. Crystal structures were obtained for ATP-PRT in complex with both substrates, and for the first time, the complete product of the reaction. These structures reveal the key features of the active site and provide insights into how substrates move into position during catalysis.

Catalytic and Anticatalytic Snapshots of a Short-Form ATP Phosphoribosyltransferase

“…Overlaying C atoms among the four structures resulted in root-mean-square deviations (Figure 2A-C) and reveal significant differences in active site interactions in comparison with other ATPPRT's. 8,13,19,[35][36] Figure 2D). This H-bond prevents PRPP from obstructing the ATP-binding site, indicating a catalytically viable binary complex, similar to that seen in the L. lactis ATPPRT-PRPP structure, 19 but contrary to the complex between PRPP and the Campylobacter jejuni ATPPRT structure.…”

Allosteric Activation Shifts the Rate-Limiting Step in a Short-Form ATP Phosphoribosyltransferase

“… 21 , 22 This mechanism has been supported by several structures of Campylobacter jejuni and M. tuberculosis ATPPRT-ATP binary complexes, 10 , 16 and by the recent structure of the C. jejuni ATPPRT catalytic core in complex with PRPP, where despite being able to bind to the free enzyme, PRPP drifts into the ATP binding site, which would lead to a dead-end complex. 33 The kinetic mechanism of HisG S ATPPRTs, on the other hand, has not been explored. We recently published the crystal structures of Pa HisG S and Pa ATPPRT in binary complexes with PRPP and PRATP, and in ternary complexes with PRPP-ATP, but were unable to obtain structures of enzyme-ATP binary complexes, suggesting a reverse order of substrate binding in comparison with HisG L ATPPRTs.…”

Host-Induced Gene Silencing of an Adenylate Kinase Gene Involved in Fungal Energy Metabolism Improves Plant Resistance to Verticillium dahliae

“…The upregulation of VdVA, VdATP6, and VdAC might also be related to ATP synthesis and the signal network [75][76][77]. When VdATP-PRT expression is strongly enhanced, glycometabolism may be stimulated and thus provide cellular energy [78][79][80]. Taken together, the accumulative evidence suggests that VdAK is a positive virulence regulator that is linked to energy metabolism.…”