Oligomeric state of hypoxanthine-guanine phosphoribosyltransferase from Mycobacterium tuberculosis.

Autor: Eng WS; School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland 4072, Australia., Keough DT; School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland 4072, Australia., Hockova D; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i. Flemingovo nam. 2, CZ-166 10 Prague 6, Czechia., Winzor DJ; School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland 4072, Australia., Guddat LW; School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland 4072, Australia. Electronic address: luke.guddat@uq.edu.au.
Jazyk: angličtina
Zdroj: Biochimie [Biochimie] 2017 Apr; Vol. 135, pp. 6-14. Date of Electronic Publication: 2017 Jan 09.
DOI: 10.1016/j.biochi.2016.12.020
Abstrakt: Sedimentation equilibrium and size-exclusion chromatography experiments on Mycobacterium tuberculosis hypoxanthine-guanine phosphoribosyltransferase (MtHGPRT) have established the existence of this enzyme as a reversibly associating mixture of dimeric and tetrameric species in 0.1 M Tris-HCl-0.012 M MgCl 2 , pH 7.4. Displacement of the equilibrium position towards the larger oligomer by phosphate signifies the probable existence of MtHGPRT as a tetramer in the biological environment. These data thus add credibility to the relevance of considering enzyme function in the light of a published tetrameric structure deduced from X-ray crystallography. Failure of 5-phospho-α-d-ribosyl-1-pyrophosphate (PRib-PP) to perturb the dimer-tetramer equilibrium position indicates the equivalence and independence of binding for this substrate (the first to bind in an ordered sequential mechanism) to the two oligomers. By virtue of the displacement of the equilibrium position towards dimer that is affected by removing MgCl 2 from the Tris-HCl buffer, it can be concluded that divalent metal ions, as well as phosphate, can affect the oligomerization. These characteristics of MtHGPRT in solution are correlated with published crystal structures of four enzyme-ligand complexes.
(Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)
Databáze: MEDLINE
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