FIGURE 1.
Predicted metal‐ion‐binding residues in the ComEC metallo‐β‐lactamase (MBL) domain. (a) A model for the metal ion (M2+) co‐ordination in the ComEC CTD based on structural similarity to the MBL family. Residue numbers are in red for the Bacillus subtilis protein and blue for the Moorella thermoacetica protein. A metal ion‐bridging hydroxide ion is the likely nucleophile in the hydrolytic reaction catalyzed by the enzyme. *indicates the residues substituted in this study. (b) Alignment of the motif II sequences of ComEC proteins and selected MBLs. Putative or established metal ion–ligating residues are shown in red. The motif positions substituted in this study are marked by red squares. Bsu, B. subtilis; CbpE, teichoic acid phosphorylesterase; Mth, M. thermoacetica; Ngo, Neisseria gonorrhoeae; Spn, Streptococcus pneumoniae; Vch, Vibrio cholerae. For a discussion of SpnComEC motif II, see the text