Fig. 3

Schematic of the YuiC active site showing the conservation with MltA. The lower barrel side shows significant conservation to MltA including the conserved catalytic aspartate and the residues allowing mechanism 2 of Powell et al. [21]. The upper face is not conserved. Substrate assisted catalysis is unlikely because S154, which is unique to YuiC is holding the acetyl carbonyl in the wrong place for this mechanism. The helix from MltA (purple) is thought to stabilise the carbenium ion. It is possible that the helix from YuiC (cyan) may play a similar role or release E98 to act as a second carboxylate, as 97–100 are disordered in the apo structure indicating flexibility in this region. The two helices are shown in their superimposed positions. Where two numbers are given the first is B.subtilis YuiC and the second E.coli MltA (2pi8 numbering)