From cyclohydrolase to oxidoreductase: Discovery of nitrile reductase activity in a common fold

Steven G. Van Lanen, John S. Reader, Manal A. Swairjo, Valérie De Crécy-Lagard, Bobby Lee, Dirk Iwata-Reuyl

Research output: Contribution to journalArticlepeer-review

96 Scopus citations

Abstract

The enzyme YkvM from Bacillus subtilis was identified previously along with three other enzymes (YkvJKL) in a bioinformatics search for enzymes involved in the biosynthesis of queuosine, a 7-deazaguanine modified nucleoside found in tRNAGUN of Bacteria and Eukarya. Genetic analysis of ykvJKLM mutants in Acinetobacter confirmed that each was essential for queuosine biosynthesis, and the genes were renamed queCDEF. QueF exhibits significant homology to the type I GTP cyclohydrolases characterized by FolE. Given that GTP is the precursor to queuosine and that a cyclohydrolase-like reaction was postulated as the initial step in queuosine biosynthesis, QueF was proposed to be the putative cyclohydrolase-like enzyme responsible for this reaction. We have cloned the queF genes from B. subtilis and Escherichia coli and characterized the recombinant enzymes. Contrary to the predictions based on sequence analysis, we discovered that the enzymes, in fact, catalyze a mechanistically unrelated reaction, the NADPH-dependentreduction of 7-cyano-7-deazaguanine to 7-aminomethyl-7-deazaguanine, a late step in the biosynthesis of queuosine. We report here in vitro and in vivo studies that demonstrate this catalytic activity, as well as preliminary biochemical and bioinformatics analysis that provide insight into the structure of this family of enzymes.

Original languageEnglish
Pages (from-to)4264-4269
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number12
DOIs
StatePublished - Mar 22 2005

Keywords

  • Modified base
  • tRNA

ASJC Scopus subject areas

  • General

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