title: Biochemical and structural characterization of the putative dihydropteroate synthase ortholog Rv1207 of Mycobacterium tuberculosis.
abstract: Dihydropteroate synthase (DHPS) is involved in de novo biosynthesis of the essential cofactor folate by catalyzing the condensation of para-aminobenzoic acid (pABA) and 6-hydroxymethyl-7,8-dihydropterin-pyrophosphate (H2PtPP). Mycobacterium tuberculosis possesses a functional DHPS (MtDHPS, Rv3608c, folP1) and, based on sequence similarities, a putative ortholog (Rv1207, folP2). Here, we demonstrate that Rv1207 shows a low H2PtPP substrate affinity and lacks enzymatic DHPS activity. However, we found dapsone, a structural analog of pABA and clinically used DHPS inhibitor, to weakly bind both proteins. To gain insights into the lack of DHPS activity of Rv1207, its three-dimensional structure was determined at 2.64 A. The overall fold of both, MtDHPS (1EYE) and Rv1207, is highly conserved and conforms to a classical triosephosphate isomerase barrel arrangement. The predicted H2PtPP-binding pocket of Rv1207 is occupied by a histidine side chain, relative to a leucine residue in MtDHPS, consistent with the low affinity for this substrate and the lack of DHPS activity. We conclude that folP2 does not encode a DHPS and therefore cannot act as bypass for folP1. The metabolic function of Rv1207 remains to be defined.
authors.affiliation: Novartis Institute for Tropical Diseases Pte Ltd, Singapore. martin.gengenbacher@novartis.com
authors.forename: Martin
authors.initials: M
authors.lastname: Gengenbacher
authors.forename: Ting
authors.initials: T
authors.lastname: Xu
authors.forename: Pornwaratt
authors.initials: P
authors.lastname: Niyomrattanakit
authors.forename: Glen
authors.initials: G
authors.lastname: Spraggon
authors.forename: Thomas
authors.initials: T
authors.lastname: Dick
mesh_terms: D003460:Crystallization; D004094:Dihydropteroate Synthase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D011994:Recombinant Proteins; D004094:Dihydropteroate Synthase