N-Acylation during Glidobactin Biosynthesis by the Tridomain Nonribosomal Peptide Synthetase Module GlbF

Glidobactins are hybrid NRPS-PKS natural products that function as irreversible proteasome inhibitors A variety of medium chain 2(E),4(E)-diene fatty acids N-acylate the peptidolactam core and contribute significantly to the potency of proteasome inhibition We have expressed the initiation NRPS module GlbF (C-A-T) in Escherichia coli and observe soluble active protein only on coexpression with the 8 kDa MbtH-like protein, GlbE Following adenylation and installation of Thr as a T-domain thioester, the starter condensation domain utilizes fatty acyl-CoA donors to acylate the Thr(1) amino group and generate the fatty acyl-Thr(1)-S-pantetheinyl-GlbF Intermediate to be used in subsequent chain elongation Previously proposed to be mediated via acyl carrier protein fatty acid donors, direct utilization of fatty acyl-CoA donors for N-acylation of T-domain tethered amino acids is likely a common strategy for chain initiation in NRPS-mediated lipopeptide biosynthesis