Format

Send to

Choose Destination

See 1 citation:

J Bacteriol. 2016 Jan 4;198(6):888-97. doi: 10.1128/JB.00832-15.

Processing of Nonconjugative Resistance Plasmids by Conjugation Nicking Enzyme of Staphylococci.

Author information

1
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA.
2
Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, USA.
3
CHIRI Biosciences Precinct, School of Biomedical Sciences, Curtin University, Bentley, WA, Australia.
4
School of Biological Sciences, University of Sydney, Sydney, NSW, Australia.
5
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina, USA redinbo@unc.edu.

Abstract

Antimicrobial resistance in Staphylococcus aureus presents an increasing threat to human health. This resistance is often encoded on mobile plasmids, such as pSK41; however, the mechanism of transfer of these plasmids is not well understood. In this study, we first examine key protein-DNA interactions formed by the relaxase enzyme, NES, which initiates and terminates the transfer of the multidrug resistance plasmid pSK41. Two loops on the NES protein, hairpin loops 1 and 2, form extensive contacts with the DNA hairpin formed at the oriT region of pSK41, and here we establish that these contacts are essential for proper DNA cleavage and religation by the full 665-residue NES protein in vitro. Second, pSK156 and pCA347 are nonconjugative Staphylococcus aureus plasmids that contain sequences similar to the oriT region of pSK41 but differ in the sequence predicted to form a DNA hairpin. We show that pSK41-encoded NES is able to bind, cleave, and religate the oriT sequences of these nonconjugative plasmids in vitro. Although pSK41 could mobilize a coresident plasmid harboring its cognate oriT, it was unable to mobilize plasmids containing the pSK156 and pCA347 variant oriT mimics, suggesting that an accessory protein like that previously shown to confer specificity in the pWBG749 system may also be involved in transmission of plasmids containing a pSK41-like oriT. These data indicate that the conjugative relaxase in trans mechanism recently described for the pWBG749 family of plasmids also applies to the pSK41 family of plasmids, further heightening the potential significance of this mechanism in the horizontal transfer of staphylococcal plasmids.

IMPORTANCE:

Understanding the mechanism of antimicrobial resistance transfer in bacteria such as Staphylococcus aureus is an important step toward potentially slowing the spread of antimicrobial-resistant infections. This work establishes protein-DNA interactions essential for the transfer of the Staphylococcus aureus multiresistance plasmid pSK41 by its relaxase, NES. This enzyme also processed variant oriT-like sequences found on numerous plasmids previously considered nontransmissible, suggesting that in conjunction with an uncharacterized accessory protein, these plasmids may be transferred horizontally via a relaxase in trans mechanism. These findings have important implications for our understanding of staphylococcal resistance plasmid evolution.

PMID:
26728193
PMCID:
PMC4772599
DOI:
10.1128/JB.00832-15
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center