Detail of PDB entry 1lf2
after one round of manual optimization (a) and the final model (b) in 2mFo − DFc electron-density maps (contoured at 2.0σ) and mFo − DFc difference density (contoured at 4.0σ). Based on the crystallization conditions described in Asojo et al. (2002), the tetrahedral difference-map peak in (a) was modelled as a sulfate. Lys238A was modelled as an arginine based on the (difference) density map contours. The H∊ of this arginine in (b) makes a hydrogen bond to the backbone carbonyl of Leu242A. The figures were created with Coot (Emsley & Cowtan, 2004) and Raster3D (Merritt & Bacon, 2007).