Crystallographic analysis of AcrB

A His-tagged derivative of the multidrug efflux pump AcrB could be crystallized in three different space groups (113, R32 and P321). Experimental MAD-phasing maps from R32 AcrB(His) crystals were obtained to a resolution of 3.5 Angstrom. Data-sets of native and substrate soaked AcrB(His) crystals were collected at the Swiss Light Source X06SA beamline up to a resolution of 2.7 Angstrom 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 R-free and average B factors in the 2.7 Angstrom model. We could not identify significant densities indicating specific antibiotic binding sites in the AcrB R32 space group datasets under the soaking conditions tested. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.