Small-angle X-ray and neutron scattering of MexR and its complex with DNA supports a conformational selection binding model

Caporaletti F, Pietras Z, Morad V, Mårtensson L, Gabel F, Wallner B, Martel A, Sunnerhagen M, Biophysical Journal (2022) DOI

SASDMH9 – Pseudomonas aeruginosa Multidrug resistance operon repressor (MexR) in complex with 34bp dsDNA binding sequence (SANS data at 0% D2O)

Multidrug resistance operon repressor
34 base pair double-stranded DNA
MWexperimental 53 kDa
MWexpected 53 kDa
VPorod 79 nm3
log I(s) 2.12×10-1 2.12×10-2 2.12×10-3 2.12×10-4
Multidrug resistance operon repressor 34 base pair double-stranded DNA small angle scattering data  s, nm-1
ln I(s)
Multidrug resistance operon repressor 34 base pair double-stranded DNA Guinier plot ln 2.12×10-1 Rg: 2.9 nm 0 (2.9 nm)-2 s2
(sRg)2I(s)/I(0)
Multidrug resistance operon repressor 34 base pair double-stranded DNA Kratky plot 1.104 0 3 sRg
p(r)
Multidrug resistance operon repressor 34 base pair double-stranded DNA pair distance distribution function Rg: 2.9 nm 0 Dmax: 7.8 nm

Data validation


Fits and models


log I(s)
 s, nm-1
Multidrug resistance operon repressor 34 base pair double-stranded DNA MONSA model

log I(s)
 s, nm-1
Multidrug resistance operon repressor 34 base pair double-stranded DNA GROMACS model

SANS data with contrast variation were collected on the D22 instrument at Institut Laue-Langevin (ILL; Grenoble, France) at the concentration of 6.2 mg/mL. In total five contrast point were measured: hydrogenated MexR (hMexR) bound to hydrogenated 34bp dsDNA (PII DNA segment) at 0, 79% v/v D2O buffer and; deuterated MexR (dMexR - 73% average non-exchangeable 2H) bound to hydrogenated 34bp dsDNA (PII DNA segment) at 0, 56, 89% D2O buffer. SAXS data of hMexR in complex with PII DNA binding region was also collected using an Anton Paar SASXess instrument (I(s) vs s, where s = 4π sin θ/λ and 2θ is the scattering angle; λ=0.154 nm) at Linköping University (Linköping, Sweden). For the SAXS measurements, approximately 40 µL of 3.12 mg/mL of protein-DNA solution was loaded into a quartz capillary and four successive 1200 second frames were collected. Matching buffer containing 20 mM sodium phosphate, 150 mM NaCl, 10 mM DTT (pH 7.1) was measured in the analogous way. Data reduction was performed with SAXS-Quant 1D software, which includes slit averaging, and normalization to absolute intensity using absolute intensity direct flux measurements, buffer-subtraction and desmearing corrections.

The SAXS/SANS data, model fits, and additional analysis are included in a downloadable zip archive. The data displayed on this entry page is of the fully hydrogenated MexR/DNA complex measured in 0% v/v D2O buffer.

Multidrug resistance operon repressor (MexR)
Mol. type   Protein
Organism   Pseudomonas aeruginosa
Olig. state   Dimer
Mon. MW   15.8 kDa
 
UniProt   P52003 (5-139)
Sequence   FASTA
 
34 base pair double-stranded DNA (34bp dsDNA)
Mol. type   DNA
Organism   synthetic construct
Olig. state   Monomer
Mon. MW   21.0 kDa
Sequence   FASTA