Crystallization and preliminary X-ray diffraction analysis of the periplasmic domain of theEscherichia coliaspartate receptor Tar and its complex with aspartate

Abstract

The cell-surface receptor Tar mediates bacterial chemotaxis toward an attractant, aspartate (Asp), and away from a repellent, Ni2+. To understand the molecular mechanisms underlying the induction of Tar activity by its ligands, theEscherichia coliTar periplasmic domain with and without bound aspartate (Asp-Tar and apo-Tar, respectively) were each crystallized in two different forms. Using ammonium sulfate as a precipitant, crystals of apo-Tar1 and Asp-Tar1 were grown and diffracted to resolutions of 2.10 and 2.40 Å, respectively. Alternatively, using sodium chloride as a precipitant, crystals of apo-Tar2 and Asp-Tar2 were grown and diffracted to resolutions of 1.95 and 1.58 Å, respectively. Crystals of apo-Tar1 and Asp-Tar1 adopted space groupP41212, while those of apo-Tar2 and Asp-Tar2 adopted space groupsP212121andC2, respectively.