FIGURE 5.
Interactions between the +2 sequon position and PglB. A, ball and stick representation of acceptor peptide (yellow) and interacting PglB residues (cyan), as observed in the X-ray structure (PDB code 3RCE). Sequon and PglB residues are labeled in black and cyan, respectively. Yellow lines indicate N and C termini of the sequon. Proposed hydrogen bonds are shown as dashed lines. B, sequence alignment of different bacterial (B), archaeal (A), and eukaryotic (E) Stt3 homologues, highlighting the conservation of Ile-572. The alignment was performed using M-Coffee (56). C, peptide binding affinities (1/Kd; left panel) and turnover rates (right panel) for DQNAT and DQNAS-containing peptides and WT, I572A, and I572V PglB, respectively. Error bars indicate the S.E. of each fit.