Multiple Complexes of Long Aliphatic N‑Acyltransferases Lead to Synthesis of 2,6-Diacylated/​2-Acyl-Substituted Glycopeptide Antibiotics, Effectively Killing Vancomycin-Resistant Enterococcus

Teicoplanin A2-2 (Tei)/A40926 is the last-line anti­biotic to treat multidrug-resistant Gram-positive bacterial infections, e.g., methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus (VRE). This class of anti­biotics is powered by the N-acyl­transferase (NAT) Orf11*/​Dbv8 through N-acylation on glucos­amine at the central residue of Tei/A40926 pseudo­aglycone. The NAT enzyme possesses enormous value in untapped applications; its advanced development is hampered largely due to a lack of structural information. In this report, we present eight high-resolution X-ray crystallo­graphic unary, binary, and ternary complexes in order to decipher the molecular basis for NAT’s functionality. The enzyme undergoes a multistage conformational change upon binding of acyl-CoA, thus allowing the uploading of Tei pseudo­aglycone to enable the acyl-transfer reaction to take place in the occlusion between the N- and C-halves of the protein. The acyl moiety of acyl-CoA can be bulky or lengthy, allowing a large extent of diversity in new derivatives that can be formed upon its transfer. Vancomycin/synthetic acyl-N-acetyl cysteamine was not expected to be able to serve as a surrogate for an acyl acceptor/​donor, respectively. Most strikingly, NAT can catalyze formation of 2-N,6-O-diacylated or C6→C2 acyl-substituted Tei analogues through an unusual 1,4-migration mechanism under stoichiometric/​solvational reaction control, wherein selected representatives showed excellent biological activities, effectively counter­acting major types (VanABC) of VRE.