Fig. 1
From: Portability of the thiolation domain in recombinant pyoverdine non-ribosomal peptide synthetases
NRPS modular structure and mode of peptide synthesis. A = adenylation domain (substrate recognition and activation), T = thiolation domain (carrier protein), C = condensation domain (peptide bond formation), E = epimerisation domain (substrate racemisation), TE = thioesterase domain (product release). Most T domains are located immediately downstream of an A domain, but they can be located upstream of three different domain types. To indicate the downstream domain, the T domains in this figure are distinguished by an additional subscript label; e.g., the T domain of the initiation module is labelled TC to indicate that it is located immediately upstream of a C domain. a Domain architecture of a three module NRPS containing an initiation module (core A-T domain structure; purple), an elongation module (core C-A-T domain structure, pictured here with an additional epimerisation domain; green) and a termination module (core C-A-T-TE domain structure; orange). (b) Biosynthesis occurs in an assembly line fashion, beginning with post-translational modification of each T domain by attachment of a 4’-phosphopantetheine (4’-pp) cofactor. The 4’-pp group functions as a flexible arm to coordinate the movement of substrates between catalytic sites. (c) The A domain within each module recognises and activates (via adenylation) a specific monomer, then attaches it to the 4′-pp group of the adjacent T domain. (d and e) In a stepwise manner, starting at the first module, each C domain catalyses peptide bond formation between the donor substrate attached to the upstream T domain and the acceptor substrate attached to the downstream T domain. Prior to this condensation reaction, each T domain may need to interact with additional tailoring domains, such as the E domain pictured in module 2, which can modify the substrate borne by each module. (f) When the peptide chain reaches the termination module, the product is released by a thioesterase (TE) domain via hydrolysis or intramolecular cyclisation. The cycle of synthesis may then repeat to generate many copies of the same peptide