4L9N

Crystal structure of MepR A103V mutant from multidrug resistant S. aureus clinical isolate

Summary for 4L9N

• Entry DOI: 10.2210/pdb4l9n/pdb
• Related: 4L9J 4L9T 4L9V 4LD5
• Descriptor: MepR, SULFATE ION (3 entities in total)
• Functional Keywords: wing-helix-turn-helix, whth, transcription repression, transcription
• Biological source: Staphylococcus aureus
• Total number of polymer chains: 2
• Total formula weight: 34194.54

Authors

Birukou, I.,Brennan, R.G. (deposition date: 2013-06-18, release date: 2013-09-11, Last modification date: 2024-02-28)

Primary citation

Birukou, I.,Tonthat, N.K.,Seo, S.M.,Schindler, B.D.,Kaatz, G.W.,Brennan, R.G.
The molecular mechanisms of allosteric mutations impairing MepR repressor function in multidrug-resistant strains of Staphylococcus aureus.
MBio, 4:e00528-e00513, 2013

PubMed Abstract: Overexpression of the Staphylococcus aureus multidrug efflux pump MepA confers resistance to a wide variety of antimicrobials. mepA expression is controlled by MarR family member MepR, which represses mepA and autorepresses its own production. Mutations in mepR are a primary cause of mepA overexpression in clinical isolates of multidrug-resistant S. aureus. Here, we report crystal structures of three multidrug-resistant MepR variants, which contain the single-amino-acid substitution A103V, F27L, or Q18P, and wild-type MepR in its DNA-bound conformation. Although each mutation impairs MepR function by decreasing its DNA binding affinity, none is located in the DNA binding domain. Rather, all are found in the linker region connecting the dimerization and DNA binding domains. Specifically, the A103V substitution impinges on F27, which resolves potential steric clashes via displacement of the DNA binding winged-helix-turn-helix motifs that lead to a 27-fold reduction in DNA binding affinity. The F27L substitution forces F104 into an alternative rotamer, which kinks helix 5, thereby interfering with the positioning of the DNA binding domains and decreasing mepR operator affinity by 35-fold. The Q18P mutation affects the MepR structure and function most significantly by either creating kinks in the middle of helix 1 or completely unfolding its C terminus. In addition, helix 5 of Q18P is either bent or completely dissected into two smaller helices. Consequently, DNA binding is diminished by 2,000-fold. Our structural studies reveal heretofore-unobserved allosteric mechanisms that affect repressor function of a MarR family member and result in multidrug-resistant Staphylococcus aureus.

PubMed: 23982071
DOI: 10.1128/mBio.00528-13

Experimental method

X-RAY DIFFRACTION (1.6 Å)