UniProt functional annotation for P04993



	UniProt functional annotation for P04993

UniProt code: P04993.

Organism: Escherichia coli (strain K12).

Taxonomy: Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacterales; Enterobacteriaceae; Escherichia.

Function: 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. In the holoenzyme this subunit contributes ssDNA-dependent ATPase and fast 5'-3' helicase activity. When added to pre-assembled RecBC greatly stimulates nuclease activity and augments holoenzyme processivity. Negatively regulates the RecA-loading ability of RecBCD. {ECO:0000269|PubMed:10197988, ECO:0000269|PubMed:10840065, ECO:0000269|PubMed:12815437, ECO:0000269|PubMed:12815438, ECO:0000269|PubMed:1535156, ECO:0000269|PubMed:16041061, ECO:0000269|PubMed:1618858, ECO:0000269|PubMed:18079176, ECO:0000269|PubMed:23851395, ECO:0000269|PubMed:7608206, ECO:0000269|PubMed:9192629, ECO:0000269|PubMed:9230304, ECO:0000269|PubMed:9448271, ECO:0000269|PubMed:9790841}.

Catalytic activity: Reaction=Exonucleolytic cleavage (in the presence of ATP) in either 5'- to 3'- or 3'- to 5'-direction to yield 5'- phosphooligonucleotides.; EC=3.1.11.5; Evidence={ECO:0000255|HAMAP- Rule:MF_01487};

Activity regulation: In isolated subunit ATPase and 5'-3' helicase activity are inhibited by non-hydrolyzable ATP analogs and EDTA (PubMed:12815438). After reacting with DNA bearing a Chi site the holoenzyme is disassembled and loses exonuclease activity, DNA unwinding and Chi-directed DNA cleavage; RecB remains complexed with ssDNA, which may prevent holoenzyme reassembly (PubMed:10197988). High levels of Mg(2+) (13 mM MgCl(2+)) or incubation with DNase allow holoenyzme reassembly, suggesting it is DNA bound to RecB that prevents reassembly (PubMed:10197988). {ECO:0000269|PubMed:10197988, ECO:0000269|PubMed:12815438, ECO:0000269|PubMed:1535156}.

Subunit: Heterotrimer of RecB, RecC and RecD. All subunits contribute to DNA-binding. {ECO:0000255|HAMAP-Rule:MF_01487, ECO:0000269|PubMed:15538360, ECO:0000269|PubMed:1618858, ECO:0000269|PubMed:18668125, ECO:0000269|PubMed:3526335}.

Domain: 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+). {ECO:0000269|PubMed:25073102}.

Disruption phenotype: Loss of RecBCD enzyme exonuclease activity, no effect on recombination proficiency or resistance to DNA-damaging agents. {ECO:0000269|PubMed:10840065, ECO:0000269|PubMed:3526335}.

Similarity: Belongs to the RecD family. {ECO:0000255|HAMAP- Rule:MF_01487}.

Annotations taken from UniProtKB at the EBI.


Organism:		Escherichia coli (strain K12).
Taxonomy:		Bacteria; Proteobacteria; Gammaproteobacteria; Enterobacterales; Enterobacteriaceae; Escherichia.



Function:		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. In the holoenzyme this subunit contributes ssDNA-dependent ATPase and fast 5'-3' helicase activity. When added to pre-assembled RecBC greatly stimulates nuclease activity and augments holoenzyme processivity. Negatively regulates the RecA-loading ability of RecBCD. {ECO:0000269\|PubMed:10197988, ECO:0000269\|PubMed:10840065, ECO:0000269\|PubMed:12815437, ECO:0000269\|PubMed:12815438, ECO:0000269\|PubMed:1535156, ECO:0000269\|PubMed:16041061, ECO:0000269\|PubMed:1618858, ECO:0000269\|PubMed:18079176, ECO:0000269\|PubMed:23851395, ECO:0000269\|PubMed:7608206, ECO:0000269\|PubMed:9192629, ECO:0000269\|PubMed:9230304, ECO:0000269\|PubMed:9448271, ECO:0000269\|PubMed:9790841}.


Catalytic activity:		Reaction=Exonucleolytic cleavage (in the presence of ATP) in either 5'- to 3'- or 3'- to 5'-direction to yield 5'- phosphooligonucleotides.; EC=3.1.11.5; Evidence={ECO:0000255\|HAMAP- Rule:MF_01487};
Activity regulation:		In isolated subunit ATPase and 5'-3' helicase activity are inhibited by non-hydrolyzable ATP analogs and EDTA (PubMed:12815438). After reacting with DNA bearing a Chi site the holoenzyme is disassembled and loses exonuclease activity, DNA unwinding and Chi-directed DNA cleavage; RecB remains complexed with ssDNA, which may prevent holoenzyme reassembly (PubMed:10197988). High levels of Mg(2+) (13 mM MgCl(2+)) or incubation with DNase allow holoenyzme reassembly, suggesting it is DNA bound to RecB that prevents reassembly (PubMed:10197988). {ECO:0000269\|PubMed:10197988, ECO:0000269\|PubMed:12815438, ECO:0000269\|PubMed:1535156}.
Subunit:		Heterotrimer of RecB, RecC and RecD. All subunits contribute to DNA-binding. {ECO:0000255\|HAMAP-Rule:MF_01487, ECO:0000269\|PubMed:15538360, ECO:0000269\|PubMed:1618858, ECO:0000269\|PubMed:18668125, ECO:0000269\|PubMed:3526335}.
Domain:		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+). {ECO:0000269\|PubMed:25073102}.
Disruption phenotype:		Loss of RecBCD enzyme exonuclease activity, no effect on recombination proficiency or resistance to DNA-damaging agents. {ECO:0000269\|PubMed:10840065, ECO:0000269\|PubMed:3526335}.
Similarity:		Belongs to the RecD family. {ECO:0000255\|HAMAP- Rule:MF_01487}.