An extracellular domain of the EsaA membrane component of the type VIIb secretion system: expression, purification and crystallization

The membrane protein EsaA is a conserved component of the type VIIb secretion system. Limited proteolysis of purified EsaA from Staphylococcus aureus USA300 identified a stable 48   kDa fragment, which was mapped by fingerprint mass spectrometry to an uncharacterized extracellular segment of EsaA. Analysis by circular dichroism spectroscopy showed that this fragment folds into a single stable domain made of mostly α -helices with a melting point of 34.5 ° C. Size-exclusion chromatography combined with multi-angle light scattering indicated the formation of a dimer of the purified extracellular domain. Octahedral crystals were grown in 0.2   M ammonium citrate tribasic pH 7.0, 16% PEG 3350 using the hanging-drop vapor-diffusion method. Diffraction data were analyzed to 4.0   Å resolution, showing that the crystals belonged to the enantiomorphic tetragonal space groups P41212 or P43212, with unit-cell parameters a = 197.5, b = 197.5, c = 368.3   Å , α = β = γ = 90 ° .
Source: Acta Crystallographica Section F - Category: Biochemistry Authors: Tags: ESAT-6-like secretion system ESS type VII secretion system EsaA extracellular domain Staphylococcus aureus USA300 research communications Source Type: research