Fig. 2. Left: Hydrogen bonding between the side chain of Asn717 and the carbonyls of substrate. We conclude these hydrogen bonds are critical in substrate recognition and explain the requirement for an l-configured non-glycine residue at position residues 7 of substrate (Phe is shown from PDB ; 4AKT). Right: PatGmac macrocyclisation substrate requirements: a heterocycle before AYD adopting a cis- or cis-like conformation, a side chain (R ≥ Me) preceding the heterocycle. We conclude two substrate carbonyls (coloured green & pink) hydrogen bonded with Asn717 are critical.
