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Publication Abstract from PubMed

The serine family of site-specific DNA recombination enzymes accomplishes strand cleavage, exchange and religation using a synaptic protein tetramer. A double-strand break intermediate in which each protein subunit is covalently linked to the target DNA substrate ensures that the recombination event will not damage the DNA. The previous structure of a tetrameric synaptic complex of gammadelta resolvase linked to two cleaved DNA strands had suggested a rotational mechanism of recombination in which one dimer rotates 180 degrees about the flat exchange interface for strand exchange. Here, we report the crystal structure of a synaptic tetramer of an unliganded activated mutant (M114V) of the G-segment invertase (Gin) in which one dimer half is rotated by 26 degrees or 154 degrees relative to the other dimer when compared with the dimers in the synaptic complex of gammadelta resolvase. Modeling shows that this rotational orientation of Gin is not compatible with its being able to bind uncleaved DNA, implying that this structure represents an intermediate in the process of strand exchange. Thus, our structure provides direct evidence for the proposed rotational mechanism of site-specific recombination.

Crystal structure of an intermediate of rotating dimers within the synaptic tetramer of the G-segment invertase.,Ritacco CJ, Kamtekar S, Wang J, Steitz TA Nucleic Acids Res. 2013 Feb 1;41(4):2673-82. doi: 10.1093/nar/gks1303. Epub 2012 , Dec 28. PMID:23275567^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.