The crystal structure of β-lactamase TEM1 from E. coli has been solved to 2.5 Å resolution by X-ray diffraction methods and refined to a crystallographic R-factor of 22.7%. The structure was determined by multiple isomorphous replacement using four heavy atom derivatives. The solution from molecular replacement, using a polyalanine model constructed from the Cα coordinates of S. Aureus PC1 enzyme, provided a set of phases used for heavy atom derivatives analysis. The E. coli β-lactamase TEM1 is made up of two domains whose topology is similar to that of the PC1 enzyme. However, global superposition or the two proteins shows significant differences.
