Mutations at serine 37 in mouse guanylate kinase confer resistance to 6-thioguanine.

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Ardiani A, Goyke A, Black ME

Mutations at serine 37 in mouse guanylate kinase confer resistance to 6-thioguanine.

Protein Eng Des Sel. 2009 Apr;22(4):225-32. doi: 10.1093/protein/gzn078. Epub 2009 Jan 10.

PubMed ID

19136674 [ View in PubMed

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Abstract

Guanylate kinase (GMK) is an essential nucleoside monophosphate kinase that catalyzes the phosphorylation of guanine-monophosphate (GMP) and dGMP to yield GDP and dGDP, respectively, important precursors for nucleotide synthesis. GMK is also responsible for the activation of 6-thioguanine (6-TG), a drug widely used as chemotherapeutic agent to treat leukemia. Several mechanisms of resistance to 6-TG have been reported but a subset of drug resistant cells cannot be explained by these mechanisms. We propose that mutations in GMK could result in drug resistance. Because cells require the presence of a functional GMK for viability, mutations that arise that lead to 6-TG resistance must retain activity toward GMP. We report three amino acid substitutions at serine 37 (S37) in mouse GMK that display activity toward GMP by conferring genetic complementation to a conditional GMK-deficient Escherichia coli and in enzyme assays. When 6-TG is included in complementation studies, cells expressing wild-type GMK are sensitive whereas all S37 mutants examined are able to effectively discriminate against 6-TG and display a drug resistance phenotype. Activity of the three S37 mutant enzymes toward clinically relevant concentrations of 6-TGMP is undetectable. Mutations in GMK, therefore, represent a previously undescribed mechanism for 6-TG resistance.

DrugBank Data that Cites this Article

Drug Enzymes

Drug	Enzyme	Kind	Organism	Pharmacological Action	Actions
Valaciclovir	Guanylate kinase	Protein	Humans	Unknown	Substrate	Details