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The restriction fold turns to the dark side: a bacterial homing endonuclease with a PD-(D/E)-XK motif.

ABSTRACT: The homing endonuclease I-Ssp6803I causes the insertion of a group I intron into a bacterial tRNA gene-the only example of an invasive mobile intron within a bacterial genome. Using a computational fold prediction, mutagenic screen and crystal structure determination, we demonstrate that this protein is a tetrameric PD-(D/E)-XK endonuclease - a fold normally used to protect a bacterial genome from invading DNA through the action of restriction endonucleases. I-Ssp6803I uses its tetrameric assembly to promote recognition of a single long target site, whereas restriction endonuclease tetramers facilitate cooperative binding and cleavage of two short sites. The limited use of the PD-(D/E)-XK nucleases by mobile introns stands in contrast to their frequent use of LAGLIDADG and HNH endonucleases - which in turn, are rarely incorporated into restriction/modification systems.

SUBMITTER: Zhao L

PROVIDER: S-EPMC1864971 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature

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The restriction fold turns to the dark side: a bacterial homing endonuclease with a PD-(D/E)-XK motif.

Zhao Lei L Bonocora Richard P RP Shub David A DA Stoddard Barry L BL

The EMBO journal 20070405 9

The homing endonuclease I-Ssp6803I causes the insertion of a group I intron into a bacterial tRNA gene-the only example of an invasive mobile intron within a bacterial genome. Using a computational fold prediction, mutagenic screen and crystal structure determination, we demonstrate that this protein is a tetrameric PD-(D/E)-XK endonuclease - a fold normally used to protect a bacterial genome from invading DNA through the action of restriction endonucleases. I-Ssp6803I uses its tetrameric assemb ...[more]

PMID: 17410205

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