Dynamics and structural changes of calmodulin upon interaction with the antagonist calmidazolium.

Léger C, Pitard I, Sadi M, Carvalho N, Brier S, Mechaly A, Raoux-Barbot D, Davi M, Hoos S, Weber P, Vachette P, Durand D, Haouz A, Guijarro JI, Ladant D, Chenal A, BMC Biol 20(1):176 (2022) Europe PMC

SASDNY3 – Calcium-bound Calmodulin complexed with Calmidazolium

MWexperimental 16 kDa
MWexpected 17 kDa
VPorod 30 nm3
log I(s) 1.28×10-2 1.28×10-3 1.28×10-4 1.28×10-5
Calmodulin-1 Calmidazolium small angle scattering data  s, nm-1
ln I(s)
Calmodulin-1 Calmidazolium Guinier plot ln 1.29×10-2 Rg: 1.7 nm 0 (1.7 nm)-2 s2
Calmodulin-1 Calmidazolium Kratky plot 1.104 0 3 sRg
Calmodulin-1 Calmidazolium pair distance distribution function Rg: 1.7 nm 0 Dmax: 5.2 nm

Data validation

Fits and models

log I(s)
 s, nm-1

log I(s)
 s, nm-1
Calmodulin-1 Calmidazolium PYMOL model

Synchrotron SAXS data from solutions of calcium-bound calmodulin in 20 mM Hepes, 150 mM NaCl, 2 mM CaCl2 in the presence of a 3-fold excess of CDZ, pH 7.4 were collected on the SWING beam line at the SOLEIL storage ring (Saint-Aubin, France) using a EIGER 4M detector at a sample-detector distance of 2.0 m and at a wavelength of λ = 0.1033 nm (I(s) vs s, where s = 4πsin θ/λ and 2θ is the scattering angle). 1320 successive 1 second frames (0.990 second exposure time / 0.010 second dead time) were collected at 15°C using size-exclusion chromatography SAXS. A 50 μl sample containing 333 µM calmodulin was injected onto a TSKgel G3000SW column (Tosoh Bioscience) and eluted at a 0.50 ml/min flow rate. Scattered intensities were converted into absolute scale (cm-1) values using the scattering of water. Molecular mass was estimated at 16.3kDa using the correlation volume Vc (Rambo, R.P. and Tainer, J. A. (2013) Nature 496(7446):477-81.).

Ab initio model and comparison with the crystal structure: Top Panel: Comparison of the experimental data (blue dots) with the calculated scattering pattern (red line) of the DENSS density distribution shown on the right. (Grant, T. D. (2018) Nat Methods 15, 191–193). Bottom panel: Comparison of the experimental data (blue dots) with the calculated scattering pattern (red line) of the crystallographic structure of Calmidazolium-bound Holo-Calmodulin (pdb 7PSZ) obtained using CRYSOL. chi2 is 1.4.

Mol. type   Protein
Organism   Homo sapiens
Olig. state   Monomer
Mon. MW   16.7 kDa
UniProt   P0DP23 (2-149)
Sequence   FASTA
Calmidazolium (CDZ)
Mol. type   Other
Olig. state   Monomer
Mon. MW   0.7 kDa
Chemical formula