Fig. 2.

Labeling of MTB and GNCA β-lactamases suggests that neither protein open an Ω-loop pocket under the conditions tested. (A and B) Structures of wild-type (WT) MTB (PDB: 2gdn) and WT GNCA (PDB: 4b88) are shown with native cysteine residues highlighted in gray. C69 is located in the region of the Ω-loop pocket for both proteins. (C) The normalized DTNB-labeling trace for WT MTB (orange circles) plateaus at one cysteine labeling. MTB C287S (light orange pentagons) shows significantly reduced labeling. (D) The normalized labeling trace for WT GNCA shows no cysteine labeling.