These include components of the oxyanion hole (backbone amino groups of Ala/Ser/Thr237 and Ser70), the adjacent disulfide bridge, as well as Asn170, Lys73 and Asn132. Interactions involving the carbapenem 6α-1R-hydroxyethyl group, and its rotameric position, were also of considerable importance, exerting their effects upon the Glu166 general base and the deacylating water molecule as well as on the residues above.