Fig. 2 |. Key structural features of CmWaaL.
a, Cavities within the CmWaaL structure. CmWaaL is shown in ribbon representation in grey, and the two cavities as a semi-transparent surface, with cavity 1 in green and cavity 2 in blue. Volumes were calculated using the Voss Volume Voxelator (3V) server30, using probes with 10 Å and 2 Å radii, corresponding to the outer and the inner probe, respectively. Und-PP (in gold) and the key arginine (R191, R242, R265) residues for CmWaaL are shown as sticks. b, Magnified view of R191 and R265 coordinating the Und-PP (in gold) within the binding pocket. The cryo-EM density assigned to bound Und-PP is displayed as a semi-transparent grey mesh. c, Functional analysis of CmWaaL ligase activity in whole cells. LPS gel showing O-antigen extension in C. metallidurans expressing CmWaaL variants (mutated CmWaaL residues are shown in blue). WaaL+ indicates expression of wild-type (WT) CmWaaL and Ø indicates empty plasmid. d, Magnified view of the Und-PP-binding pocket in the apo structure (pink) and the Und-PP-bound structure (grey), superimposed, showing R139, R191, R242 and R265 in sticks with CPK colouring.