Crystallographic analysis of AcrB

Abstract

A His-tagged derivative of the multidrug efflux pump AcrB could be crystallized in three different space groups (R3, R32 and P321). Experimental MAD-phasing maps from R32 AcrBHis crystals were obtained to a resolution of 3.5 Å. Datasets of native and substrate soaked AcrBHis crystals were collected at the Swiss Light Source X06SA beamline up to a resolution of 2.7 Å and refinement of these data provided good quality electron density maps, which allowed us to complement the published AcrB structure (PDB code 1iwg). Introduction of amino acids 860–865 and 868 lacking in the 1iwg structure and deletion of a highly disordered region (amino acids 669–678) improved Rfree and average B factors in the 2.7 Å model. We could not identify significant densities indicating specific antibiotic binding sites in the AcrB R32 space group datasets under the soaking conditions tested