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Title: Role of W181 in modulating kinetic properties of Plasmodium falciparum hypoxanthine guanine xanthine phosphoribosyltransferase
Authors: Roy, Sourav
Karmakar, Tarak
Nagappa, Lakshmeesha K.
Rao, Vasudeva S. Prahlada
Balasubramanian, Sundaram
Balaram, Hemalatha
Keywords: Biochemistry & Molecular Biology
point mutation
molecular dynamics simulations
dynamic cross-correlations
Acyclic Nucleoside Phosphonates
Site-Directed Mutagenesis
Configurational Entropy
Flexible Loop
Issue Date: 2016
Publisher: Wiley-Blackwell
Citation: Roy, S.; Karmakar, T.; Nagappa, L. K.; Rao, V. S. P.; Balasubramanian, S.; Balaram, H., Role of W181 in modulating kinetic properties of Plasmodium falciparum hypoxanthine guanine xanthine phosphoribosyltransferase. Proteins-Structure Function and Bioinformatics 2016, 84 (11), 1658-1669
Proteins-Structure Function and Bioinformatics
Abstract: Hypoxanthine-guanine-xanthine phosphoribosyltransference (HGXPRT), a key enzyme in the purine salvage pathway of the malarial parasite, Plasmodium falciparum (Pf), catalyses the conversion of hypoxanthine, guanine, and xanthine to their corresponding mononucleotides; IMP, GMP, and XMP, respectively. Out of the five active site loops (I, II, III, III', and IV) in PfHGXPRT, loop III' facilitates the closure of the hood over the core domain which is the penultimate step during enzymatic catalysis. PfHGXPRT mutants were constructed wherein Trp 181 in loop III' was substituted with Ser, Thr, Tyr, and Phe. The mutants (W181S, W181Y and W181F), when examined for xanthine phosphoribosylation activity, showed an increase in K-m for PRPP by 2.1-3.4 fold under unactivated condition and a decrease in catalytic efficiency by more than 5-fold under activated condition as compared to that of the wild-type enzyme. The W181T mutant showed 10-fold reduced xanthine phosphoribosylation activity. Furthermore, molecular dynamics simulations of WT and in silico W181S/Y/F/T PfHGXPRT mutants bound to IMP.PPi.Mg2+ have been carried out to address the effect of the mutation of W181 on the overall dynamics of the systems and identify local changes in loop III'. Dynamic cross-correlation analyses show a communication between loop III' and the substrate binding site. Differential cross-correlation maps indicate altered communication among different regions in the mutants. Changes in the local contacts and hydrogen bonding between residue 181 with the nearby residues cause altered substrate affinity and catalytic efficiency of the mutant enzymes. Proteins 2016; 84:1658-1669. (c) 2016 Wiley Periodicals, Inc.
Description: Restricted Access
ISSN: 0887-3585
Appears in Collections:Research Articles (Balasubramanian Sundaram)
Research Papers (Hemalatha Balaram)

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