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A putative house‐cleaning enzyme encoded within an integron array: 1.8 Å crystal structure defines a new MazG subtype
Author(s) -
Robinson Andrew,
Guilfoyle Amy P.,
Harrop Stephen J.,
Boucher Yan,
Stokes H. W.,
Curmi Paul M. G.,
Mabbutt Bridget C.
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.05932.x
Subject(s) - biology , integron , gene , gene cassette , context (archaeology) , genetics , computational biology , mobile genetic elements , function (biology) , plasmid , paleontology
Summary Mobile gene cassettes collectively contain a highly diverse pool of novel genes that encode many novel adaptive functions. In the non‐clinical context, the function of almost all of the encoded proteins remains unknown despite the enormous size of this mobile gene pool. We have been characterizing cassette arrays by taking advantage of the fact that they cluster at discrete sites in chromosomes; even large arrays are thus recoverable in a relatively small number of clones in genomic libraries. In one assembled array of 116 cassettes from the marine bacterium Vibrio sp. DAT722, a putative MazG protein is encoded within the 21st cassette. Because MazG proteins are implicated in a number of cellular processes, including house‐cleaning and stress survival, the presence of such a protein in a mobile cassette was noteworthy. Here we solve the crystal structure of this α‐helical protein, and define both open and closed states of a new variant of the MazG family. Functional assays confirm that the protein is a dNTP pyrophosphohydrolase, with marked preferences for dCTP and dATP. We hypothesize that i MazG acts as a house‐cleaning enzyme, preventing the incorporation of damaging non‐canonical nucleotides into host‐cell DNA.