RecBCD enzyme subunit RecB - P08394 (RECB_ECOLI)


Protein Feature View of PDB entries mapped to a UniProtKB sequence  

A helicase/nuclease that prepares dsDNA breaks (DSB) for recombinational DNA repair. Binds to DSBs and unwinds DNA via a rapid (>1 kb/second) and highly processive (>30 kb) ATP-dependent bidirectional helicase. Unwinds dsDNA until it encounters a Chi (crossover hotspot instigator, 5'-GCTGGTGG-3') sequence from the 3' direction. Cuts ssDNA a few nucleotides 3' to Chi site, by nicking one strand or switching the strand degraded (depending on the reaction conditions). The properties and activities of the enzyme are changed at Chi. The Chi-altered holoenzyme produces a long 3'-ssDNA overhang which facilitates RecA-binding to the ssDNA for homologous DNA recombination and repair. Holoenzyme degrades any linearized DNA that is unable to undergo homologous recombination (PubMed:4562392, PubMed:4552016, PubMed:123277). In the holoenzyme this subunit contributes ATPase, 3'-5' helicase, exonuclease activity and loads RecA onto ssDNA. The RecBC complex requires the RecD subunit for nuclease activity, but can translocate along ssDNA in both directions. UniProt
Catalytic Activity
Exonucleolytic cleavage in the presence of ATP in either 5'- to 3'- or 3'- to 5'-direction to yield 5'-phosphooligonucleotides. UniProt
Pathway Maps
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Subunit Structure
Heterotrimer of RecB, RecC and RecD. All subunits contribute to DNA-binding. The C-terminus interacts with RecA (PubMed:16483938). Interacts with YgbT (Cas1) (PubMed:21219465). UniProt
The holoenzyme may undergo conformational shifts upon DNA binding: the nuclease domain of RecB may swing away from the DNA exit tunnel in RecC. When Chi DNA binds to the RecC tunnel, the nuclease domain may then swing back to its original position (that seen in crystal structures), allowing it to nick the DNA 3' of the Chi site and then rotate to load RecA. At high Mg(2+) the nuclease domain may swing back more frequently, explaining differences seen in assays performed at high Mg(2+). UniProt
  • Other Gene names: recB, ior, rorA, b2820, JW2788
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