Roles of two large serine recombinases in mobilizing the methicillin-resistance cassette SCCmec.
Mol Microbiol
; 88(6): 1218-29, 2013 Jun.
Article
in En
| MEDLINE
| ID: mdl-23651464
ABSTRACT
Methicillin-resistant Staphylococcus aureus (MRSA) emerged via acquisition of a mobile element, staphylococcal cassette chromosome mec (SCCmec). Integration and excision of SCCmec is mediated by an unusual site-specific recombination system. Most variants of SCCmec encode two recombinases, CcrA and CcrB, that belong to the large serine family. Since CcrA and CcrB are always found together, we sought to address their specific roles. We show here that CcrA and CcrB can carry out both excisive and integrative recombination in Escherichia coli in the absence of any host-specific or SCCmec-encoded cofactors. CcrA and CcrB are promiscuous in their substrate choice they act on many non-canonical pairs of recombination sites in addition to the canonical ones, which may explain tandem insertions into the SCCmec attachment site. Moreover, CcrB is always required, but CcrA is only required if one of the four half-sites is present. Recombinational activity correlates with DNA binding CcrA recognizes only that half-site, which overlaps a conserved coding frame on the host chromosome. Therefore, we propose that CcrA serves as a specificity factor that emerged through modular evolution to enable recognition of a bacterial recombination site that is not an inverted repeat.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Recombination, Genetic
/
Multigene Family
/
Methicillin Resistance
/
Recombinases
/
Methicillin-Resistant Staphylococcus aureus
Language:
En
Journal:
Mol Microbiol
Journal subject:
BIOLOGIA MOLECULAR
/
MICROBIOLOGIA
Year:
2013
Document type:
Article
Affiliation country:
Estados Unidos