Comparative studies of the low-resolution structure of two p23 co-chaperones for Hsp90 identified in Plasmodium falciparum genome.

Silva NSM, Seraphim TV, Minari K, Barbosa LRS, Borges JC, Int J Biol Macromol 2017 Nov 27; PubMed

SASDC65 – Plasmodium falciparum p23B

Co-chaperone p23
MWexperimental 32 kDa
MWexpected 31 kDa
log I(s) 1.97×10-2 1.97×10-3 1.97×10-4 1.97×10-5
Co-chaperone p23 small angle scattering data  s, nm-1
ln I(s)
Co-chaperone p23 Guinier plot ln 1.98×10-2 Rg: 3.7 nm 0 (3.7 nm)-2 s2
Co-chaperone p23 Kratky plot 1.104 0 3 sRg
Co-chaperone p23 pair distance distribution function Rg: 4.0 nm 0 Dmax: 13 nm

Experimental data validation

Fits and models

log I(s)
 s, nm-1
Co-chaperone p23 DAMFILT model
Small angle X-ray scattering measurements (SAXS) were performed at the SAXS2 beamline located at the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, São Paulo, Brazil. The X-ray scattering data (I(s) vs s, where s = 4πsinθ/λ and 2θ is the scattering angle; λ = 0.1488 nm) were acquired using a two-dimension position-sensitive MARR-CCD detector and a sample-to-detector distance of ~1000 mm, corresponding to the q-range 0 < q < 0.35. In order to checking for protein aggregation or concentration-dependent effects, samples were prepared at various protein concentrations (2 mg/mL and 3 mg/mL) in 25 mM Tris-HCl (pH 7.5) buffer, containing 150 mM NaCl, 2 mM EDTA and 1 mM β-mercaptoethanol. Samples were exposed to X-ray at different time frames (5 x 30 seconds, and 180 seconds) to investigate for X-ray damage. No effects of protein concentration or X-ray damage were detected. The model depicts the averaged spatial representation of the protein (DAMFILT occupancy and volume-corrected bead model).

Co-chaperone p23 (Pfp23B)
Mol. type   Protein
Organism   Plasmodium falciparum (isolate 3D7)
Olig. state   Monomer
Mon. MW   30.9 kDa
UniProt   Q8IKU1
Sequence   FASTA