Synchrotron SAXS data from solutions of BusR in 200mM NaCl, 30 mM HEPES , 3% (v/v) glycerol, pH 7.5 were collected on the EMBL P12 beam line at PETRA III (DESY, Hamburg, Germany) using a Pilatus 6M detector at a sample-detector distance of 3 m and at a wavelength of λ = 0.123981 nm (I(s) vs s, where s = 4πsinθ/λ, and 2θ is the scattering angle). In-line size-exclusion chromatography (SEC) SAS was employed. The SEC parameters were as follows: A 50.00 μl sample at 6 mg/ml was injected at a 0.25 ml/min flow rate onto a GE Superdex 200 Increase 5/150 column at 20°C. 1800 successive 0.495 second frames were collected. The data were normalized to the intensity of the transmitted beam and radially averaged; the scattering of the solvent-blank was subtracted.