RuvABC is well-studied. The description from Wikipedia is as follows:

RuvABC is a complex of three proteins that mediate branch migration and resolve the Holliday junction created during recombination repair.

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 binding of the RuvC protein to the RuvAB complex is thought to cleave the DNA strands, thereby resolving the Holliday junction.

The structure of the complex has been variously elucidated through X-ray crystallography 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.

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. 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.
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This subsystem is more about the other gene that often clusters with ruvABC. The gene is often annotated as "Concerved hypothetical protein yebC". However, this name for the gene actually is used to describe a number of distinct functions (in my opinion), so I have elected to use instead

FIG000859: hypothetical protein

This is simply a name for a functional role that I do not yet understand. However, I am deeply
convinced that there is some relationship between the role of this gene and RuvABC. Hence, I
think that the gene is probably related to recombination.

There are two things to note about this subsystem:

1. The functional role "FIG000859: hypothetical protein"
is deeply related to RuvABC based on chromosomal clustering evidence.

2. RuvC is missing in many entries

The variant codes are as follows:

1 => the hypothetical is present with all three Ruv genes
2 => the hypothetical is present with at least 2 of the Ruv genes

Either RuvC is not essential, or there is a substitute that I have not yet been able to identify.

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The following short extract is from

Holliday Junction Processing in Bacteria: Insights from the Evolutionary Conservation of RuvABC, RecG, and RusA

Gary J. Sharples, Stuart M. Ingleston, and Robert G. Lloyd

Journal of Bacteriology, September 1999, p. 5543-5550, Vol. 181, No. 18

CONSERVATION OF RUVABC IN BACTERIA

"Genes encoding homologs of RuvA and RuvB are widespread in bacteria, whereas homologs of RuvC are less common (Fig. 3). The ruvA and ruvB genes are often found together in an operon, sometimes including ruvC upstream, although there are cases, such as in Synechocystis, where the three ruv genes are scattered around the genome in separate operons. RuvC is absent from the completed genomes of Mycoplasma genitalium, Mycoplasma pneumoniae, Bacillus subtilis, and Borrelia burgdorferi and has yet to be found in Enterococcus, Streptococcus, and Clostridium spp. (Fig. 3). A phylogenetic tree based on 16S rRNA sequences shows that Mycoplasma, Streptococcus, Enterococcus, Clostridium, and Bacillus spp. define a branch of the tree that seems to lack RuvC (Fig. 4). The absence of RuvC from B. burgdorferi is puzzling, especially as it is present in the related spirochete Treponema pallidum. As some of these genomes contain the Holliday junction resolvase RusA (Fig. 3), they could be using this enzyme instead. However, several organisms have neither RuvC nor RusA, suggesting the existence of an alternative Holliday junction resolvase whose nature has yet to be described. It would seem incongruous to have the enzymes to move Holliday junctions (RuvAB) but lack the means to resolve them."
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The conjecture we mentioned was arrived at earlier in the following paper:


Nucleic Acids Res. 2004; 32(8): 2353–2361.
Published online 2004 April 30. doi: 10.1093/nar/gkh555.


Identification and functional analysis of ‘hypothetical’ genes expressed in Haemophilus influenzae
Eugene Kolker, Kira S. Makarova, Svetlana Shabalina,1 Alex F. Picone, Samuel Purvine, Ted Holzman, Tim Cherny, David Armbruster,2 Robert S. Munson, Jr, Grigory Kolesov, Dmitrij Frishman, and Michael Y. Galperin1


"Likewise, the structures of HI0315 (YebC) homologs from Aquifex aeolicus (43) and E.coli failed to suggest the function for this protein, encoded in every bacterium except Buchnera. Nevertheless, the conserved association of the yebC gene with ruvABC genes, encoding three subunits of the Holliday junction resolvasome, coupled with the universal presence of this gene in all bacteria (except Buchnera) leave little doubt that HI0315 protein is somehow involved in the same process. Since the yebC gene appears to be non-essential in H.influenzae (Table 1S), it could encode an auxiliary component of the resolvasome that plays a role in DNA replication or, less likely, DNA transcription."