The ripX locus of Bacillus subtilis encodes a site-specific recombinase involved in proper chromosome partitioning.
The Bacillus subtilis ripX gene encodes a protein that has 37 and 44% identity with the XerC and XerD site-specific recombinases of Escherichia coli. XerC and XerD are hypothesized to act in concert at the dif site to resolve dimeric chromosomes formed by recombination during replication. Cultures of ripX mutants contained a subpopulation of unequal-size cells held together in long chains. The chains included anucleate cells and cells with aberrantly dense or diffuse nucleoids, indicating a chromosome partitioning failure. This result is consistent with RipX having a role in the resolution of chromosome dimers in B. subtilis. Spores contain a single uninitiated chromosome, and analysis of germinated, outgrowing spores showed that the placement of FtsZ rings and septa is affected in ripX strains by the first division after the initiation of germination. The introduction of a recA mutation into ripX strains resulted in only slight modifications of the ripX phenotype, suggesting that chromosome dimers can form in a RecA-independent manner in B. subtilis. In addition to RipX, the CodV protein of B. subtilis shows extensive similarity to XerC and XerD. The RipX and CodV proteins were shown to bind in vitro to DNA containing the E. coli dif site. Together they functioned efficiently in vitro to catalyze site-specific cleavage of an artificial Holliday junction containing a dif site. Inactivation of codV alone did not cause a discernible change in phenotype, and it is speculated that RipX can substitute for CodV in vivo.
Sciochetti
S A
SA
Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
Piggot
P J
PJ
Sherratt
D J
DJ
Blakely
G
G
D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004254:DNA Nucleotidyltransferases / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D019426:Integrases; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011938:Rec A Recombinases / Q000235:genetics; D045522:Recombinases; D011995:Recombination, Genetic; D013014:SOS Response, Genetics / Q000235:genetics; D013171:Spores, Bacterial; D013379:Substrate Specificity
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D045522:Recombinases; C473360:XerC protein, E coli; C121793:codV protein, Bacillus subtilis; D004254:DNA Nucleotidyltransferases; D019426:Integrases; D011938:Rec A Recombinases; C473361:XerD protein, E coli; C115006:integron integrase IntI1