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Biochim Biophys Acta Proteins Proteom. 2018 Feb;1866(2):264-274. doi: 10.1016/j.bbapap.2017.08.018. Epub 2017 Aug 26.

Anthranilate phosphoribosyltransferase: Binding determinants for 5'-phospho-alpha-d-ribosyl-1'-pyrophosphate (PRPP) and the implications for inhibitor design.

Author information

1
Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Biological Sciences, University of Auckland, 3 Symonds Street, Auckland 1142, New Zealand. Electronic address: g.evans@auckland.ac.nz.
2
Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Chemical Sciences, University of Auckland, 23 Symonds Street, Auckland 1142, New Zealand.
3
Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; Biomolecular Interaction Centre, University of Canterbury, P. O. Box 4800, Christchurch 8140, New Zealand; Department of Chemistry, University of Canterbury, P. O. Box 4800, Christchurch 8140, New Zealand.
4
Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Biological Sciences, University of Auckland, 3 Symonds Street, Auckland 1142, New Zealand.
5
Maurice Wilkins Centre for Molecular Biodiscovery and School of Biological Sciences, University of Auckland, 3A Symonds Street, Auckland 1142, New Zealand; School of Biological Sciences, University of Auckland, 3 Symonds Street, Auckland 1142, New Zealand. Electronic address: s.lott@auckland.ac.nz.

Abstract

Phosphoribosyltransferases (PRTs) bind 5'-phospho-α-d-ribosyl-1'-pyrophosphate (PRPP) and transfer its phosphoribosyl group (PRib) to specific nucleophiles. Anthranilate PRT (AnPRT) is a promiscuous PRT that can phosphoribosylate both anthranilate and alternative substrates, and is the only example of a type III PRT. Comparison of the PRPP binding mode in type I, II and III PRTs indicates that AnPRT does not bind PRPP, or nearby metals, in the same conformation as other PRTs. A structure with a stereoisomer of PRPP bound to AnPRT from Mycobacterium tuberculosis (Mtb) suggests a catalytic or post-catalytic state that links PRib movement to metal movement. Crystal structures of Mtb-AnPRT in complex with PRPP and with varying occupancies of the two metal binding sites, complemented by activity assay data, indicate that this type III PRT binds a single metal-coordinated species of PRPP, while an adjacent second metal site can be occupied due to a separate binding event. A series of compounds were synthesized that included a phosphonate group to probe PRPP binding site. Compounds containing a "bianthranilate"-like moiety are inhibitors with IC50 values of 10-60μM, and Ki values of 1.3-15μM. Structures of Mtb-AnPRT in complex with these compounds indicate that their phosphonate moieties are unable to mimic the binding modes of the PRib or pyrophosphate moieties of PRPP. The AnPRT structures presented herein indicated that PRPP binds a surface cleft and becomes enclosed due to re-positioning of two mobile loops.

KEYWORDS:

Metal catalyzed transferases; Mg(2+) chelated substrates; PRT inhibitors; Phosphonate inhibitors; Phosphoribosylpyrophosphate; Phosphoribosyltransferase

PMID:
28844746
DOI:
10.1016/j.bbapap.2017.08.018
[Indexed for MEDLINE]

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