Fig. 5: Overview of the essential role of the bifunctional TEII, LgnA, in the legonindolizidine A 6 NRPS assembly line. | Nature Communications

Fig. 5: Overview of the essential role of the bifunctional TEII, LgnA, in the legonindolizidine A 6 NRPS assembly line.

From: Aminoacyl chain translocation catalysed by a type II thioesterase domain in an unusual non-ribosomal peptide synthetase

Fig. 5

a LgnA catalyses L-Thr unit transaminoacylation reaction between LgnB-T0 and LgnD-T1 domain. The correct intermediate, LgnD-T1-bound L-Thr, undergoes the first condensation with IV-CoA to yield LgnD-T1-bound IV-Thr, followed by the C2-catalysed dehydration on L-Thr residue to provide LgnD-T1-tethered IV-Dhb for the downstream pathway. Due to the nonselective condensation reaction, LgnB-T0-bound L-Thr reacts with IV-CoA to generate the aberrant intermediate, LgnB-T0-bound IV-Thr. LgnA plays the editing role of removing LgnD-T0-bound IV-Thr to regenerate the holo-LgnB. However, the nonselective condensation domain could catalyse the reaction between LgnB-T0-tethered IV-Thr and the downstream L-Pro unit to generate the “dead-end” intermediate protein-tethered IV-Thr-Pro. b Phylogenetic analysis indicates that LgnA and LgnA-like TEII CDSs form a distinct clade from typical TEII enzymes, TEI domains, and known aminoacyltransferases in NRPSs. A maximum likelihood tree containing bootstrap values was generated using MEGA 7.0.26. The sequence information for thioesterases and aminoacyltransferases used in this analysis are listed in Supplementary Table 4.

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