Figure 6.

(A) Model of the CWSS peptide structure from the SaSrtA–LPAT* complex on the substrate binding surface of BaSrtC. The peptide (green) is taken from the SaSrtA–LPAT* structure without modification. Active site residues are indicated along with the potential Ser¹¹⁴ binding site. The hydroxyl oxygen of Ser¹¹⁴ (Ser¹¹⁴ is colored gray, while its OH group is colored white) comes into close contact with the side chain of position X. (B) Close-up overlay of the BaSrtC structure (green) with apo-SaSrtA (red, left), holo-SaSrtA (blue, center), and apo-BaSrtA (orange, right). Active site arginine, cysteine, and histidine residues are denoted. The active site residues of apo-BaSrtC overlay best with those of holo-SaSrtA (SaSrtA–LPAT*).