CRYSTALLIZATION AND PRELIMINARY CRYSTALLOGRAPHIC STUDY OF A COMPONENTOF THE ESCHERICHIA-COLI TOL SYSTEM - TOLB

TolB from Escherichia coli is part of the Tol system used by the group A colicins to penetrate and kill cells. A TolB derivative tagged with six histidines was overexpressed, purified by chelation on a nickel a ffinity column and crystallized using the SAmBA software to define the optimal crystallization protocol. The crystals belong to the monoclin ic system, space group P2(1) with unit-cell parameters a = 64.48, b = 41.06, c = 78.41 Angstrom, beta = 110.78 degrees. Frozen crystals diff ract to 1.9 Angstrom resolution. Screening for heavy-atom derivatives both on the native TolB and various cysteine-substituted mutants is in progress. In addition, a selenomethionine-substituted protein is bein g produced in order to use the MAD method for structure determination.