Crystallization and preliminary X-ray crystallographic analysis of the N-terminal domain of XpsE protein from Xanthomonas campestris, an essential component of the type II protein-secretion machinery

Secretion of pre‐folded extracellular proteins across the outer membrane of Gram‐negative bacteria is mainly assisted by the type II secretion machinery composed of 12–15 proteins. Here, the crystallization and preliminary analysis of one of the essential components of Xanthomonas campestris secretion machinery, the 21 kDa N‐terminal domain of XpsE protein (XpsEN), are reported. XpsEN has been crystallized at 277 K using PEG 400 as precipitant. These crystals belong to the tetragonal space group P41212 (or P43212), with unit‐cell parameters a = b = 56.1, c = 102.7 Å. A 98.5% complete native data set from a frozen crystal has been collected to 2.0 Å resolution at 100 K with an overall Rmerge of 5.0%. The presence of one subunit of XpsEN per asymmetric unit gives a crystal volume per protein weight (VM) of 1.92 Å3 Da−1 and a solvent content of 36.1%.