5UDG

Mutant E97Q crystal structure of Bacillus subtilis QueF with a disulfide Cys 55-99

Summary for 5UDG

• Entry DOI: 10.2210/pdb5udg/pdb
• Related: 4F8B 4FGC
• Descriptor: NADPH-dependent 7-cyano-7-deazaguanine reductase, MAGNESIUM ION, TRIETHYLENE GLYCOL, ... (4 entities in total)
• Functional Keywords: tunnel fold, disulfide inactivation, trna modification pathway, nadph-dependent reduction of the nitrile group, oxidoreductase
• Biological source: Bacillus subtilis
• Cellular location: Cytoplasm : A0A063X9I2
• Total number of polymer chains: 5
• Total formula weight: 87008.68

Authors

Mohammad, A.,Kiani, M.K.,Iwata-Reuyl, D.,Stec, B.,Swairjo, M. (deposition date: 2016-12-27, release date: 2017-03-29, Last modification date: 2024-10-16)

Primary citation

Mohammad, A.,Bon Ramos, A.,Lee, B.W.,Cohen, S.W.,Kiani, M.K.,Iwata-Reuyl, D.,Stec, B.,Swairjo, M.A.
Protection of the Queuosine Biosynthesis Enzyme QueF from Irreversible Oxidation by a Conserved Intramolecular Disulfide.
Biomolecules, 7:-, 2017

PubMed Abstract: QueF enzymes catalyze the nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reduction of the nitrile group of 7-cyano-7-deazaguanine (preQ₀) to 7-aminomethyl-7-deazaguanine (preQ₁) in the biosynthetic pathway to the tRNA modified nucleoside queuosine. The QueF-catalyzed reaction includes formation of a covalent thioimide intermediate with a conserved active site cysteine that is prone to oxidation in vivo. Here, we report the crystal structure of a mutant of QueF, which reveals an unanticipated intramolecular disulfide formed between the catalytic Cys55 and a conserved Cys99 located near the active site. This structure is more symmetric than the substrate-bound structure and exhibits major rearrangement of the loops responsible for substrate binding. Mutation of Cys99 to Ala/Ser does not compromise enzyme activity, indicating that the disulfide does not play a catalytic role. Peroxide-induced inactivation of the wild-type enzyme is reversible with thioredoxin, while such inactivation of the Cys99Ala/Ser mutants is irreversible, consistent with protection of Cys55 from irreversible oxidation by disulfide formation with Cys99. Conservation of the cysteine pair, and the reported in vivo interaction of QueF with the thioredoxin-like hydroperoxide reductase AhpC in suggest that regulation by the thioredoxin disulfide-thiol exchange system may constitute a general mechanism for protection of QueF from oxidative stress in vivo.

PubMed: 28300774
DOI: 10.3390/biom7010030

Experimental method

X-RAY DIFFRACTION (2.5 Å)