Small-angle X-ray scattering structural insights into alternative pathway of actin oligomerization associated with inactivated state

Ryzhykau Y, Povarova O, Dronova E, Kuklina D, Antifeeva I, Ilyinsky N, Okhrimenko I, Semenov Y, Kuklin A, Ivanovich V, Fonin A, Uversky V, Turoverov K, Kuznetsova I, Biochemical and Biophysical Research Communications :149340 (2023) DOI

SASDT25 – G- / I-actin mixture - Skeletal muscle actin from Oryctolagus cuniculus: mixture of globular actin monomers and inactivated actin monomers and dimers

Actin, alpha skeletal muscle
MWexperimental 61 kDa
MWexpected 42 kDa
VPorod 84 nm3
log I(s) 3.39×10-1 3.39×10-2 3.39×10-3 3.39×10-4
Actin, alpha skeletal muscle small angle scattering data  s, nm-1
ln I(s)
Actin, alpha skeletal muscle Guinier plot ln 3.39×10-1 Rg: 3.1 nm 0 (3.1 nm)-2 s2
(sRg)2I(s)/I(0)
Actin, alpha skeletal muscle Kratky plot 1.104 0 √3 sRg
p(r)
Actin, alpha skeletal muscle pair distance distribution function Rg: 3.4 nm 0 Dmax: 12 nm

Data validation

Fits and models

log I(s)
 s, nm-1
Actin, alpha skeletal muscle OTHER [STATIC IMAGE] model
SAXS data from solutions of a G- / I-actin mixture from Oryctolagus cuniculus (a mixture of globular actin monomers and inactivated actin monomers/dimers) in 5 mM Tris, 0.1 mM CaCl2, 1 mM NaN3, 0.2 mM ATP, pH 8.1 were collected using a Rigaku MicroMax 007-HF instrument at the Moscow Institute of Physics and Technology (MIPT; Dolgoprudny, Russian Federation) equipped with a multiwire gas-filled ASM DTR Triton 200 detector at a sample-detector distance of 2 m and at a wavelength of λ = 0.15406 nm (I(s) vs s, where s = 4πsinθ/λ, and 2θ is the scattering angle). One solute concentration of 1.25 mg/ml was measured at 20°C. One 3600 second frame was collected. The data were normalized to the intensity of the transmitted beam and radially averaged; the scattering of the solvent-blank was subtracted.

One week incubation of G-actin leads to formation of mixture of G-actin monomers and I-actin monomers and dimers. The exact structures of I-actin monomers and dimers are unknown. However, using the values of Rg and Vp, volume fraction of dimers and distance Dm-m between the centres of two monomers in these dimers we found to be equal to 4.6 ± 2.1, and 5.1 ± 1.4 nm, respectively.

Actin, alpha skeletal muscle
Mol. type   Protein
Organism   Oryctolagus cuniculus
Olig. state   Monomer
Mon. MW   42.1 kDa
 
UniProt   P68135 (1-377)
Sequence   FASTA
 
PDB ID   3HBT