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 A+ and re¢nement 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 signi¢cant densities indicating speci¢c antibiotic binding sites in the AcrB R32 space group datasets under the soaking conditions tested.