RuvABC (
Recombination UV) is a complex of three
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s that mediate
branch migration and resolve the
Holliday junction created during
homologous recombination
Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
in bacteria. As such, RuvABC is critical to bacterial
DNA repair
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA da ...
.
RuvA and RuvB bind to the four strand DNA structure
formed in the Holliday junction intermediate, and migrate the strands through each other, using a putative spooling mechanism. The RuvAB complex can carry out DNA helicase activity, which helps unwind the duplex DNA. The binding of the RuvC protein to the RuvAB complex is thought to cleave the DNA strands, thereby resolving the Holliday junction.
RuvA is a DNA-binding protein that binds Holliday junctions with high affinity. The structure of the complex has been variously elucidated through
X-ray crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
and EM data, and suggest that the complex consists of either one or two RuvA tetramers, with charge lined grooves through which the incoming DNA is channelled. The structure also showed the presence of so-called 'acidic pins' in the centre of the tetramer, which serve to separate the DNA duplexes. Its crystal structure has been solved at 1.9A.
RuvB is an ATPase that is only active in the presence of DNA and compared to RuvA, RuvB has a low affinity for DNA. The RuvB proteins are thought to form hexameric rings on the exit points of the newly formed DNA duplexes, and it is proposed that they 'spool' the emerging DNA through the RuvA tetramer.
RuvC is the resolvase, which cleaves the Holliday junction. RuvC proteins have been shown to form dimers in solution and its structure has been solved at 2.5A. It is thought to bind either on the open, DNA exposed face of a single RuvA tetramer, or to replace one of the two tetramers. Binding is proposed to be mediated by an unstructured loop on RuvC, which becomes structured on binding RuvA. RuvC can be bound to the complex in either orientation, therefore resolving Holliday junctions in either a horizontal or vertical manner.
See also
*
RecBCD
Exodeoxyribonuclease V (EC 3.1.11.5, RecBCD, Exonuclease V, ''Escherichia coli'' exonuclease V, ''E. coli'' exonuclease V, gene recBC endoenzyme, RecBC deoxyribonuclease, gene recBC DNase, gene recBCD enzymes) is an enzyme of ''E. coli'' that ini ...
References
Further reading
*
*
*Eggleston AK, Mitchell AH, and West SC (1997). “In Vitro Reconstitution of the Late Steps of Genetic Recombination in E. coli”. Cell. 89: 607–617.
External links
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Proteins
{{Protein-stub