BLAST analysis. (A) Domain organization of TPS: Different colors depict discrete modules. Each module contains three catalytic domains shown in the same color, as well as the C-terminal containing 422 amino acids, which were investigated in detail; A: Adenylation domain; C: Condensation domain; T: Thiolation domain; KS: Ketoacyl synthase; AT: Acyl transferase; ACP: Acyl carrier protein. (B) Phylogenetic tree of the characterized NRPS proteins: The neighbor-joining algorithm was used to infer the topology based on multiple sequence alignment and Poisson distances. Bootstrap scores of >50% are presented. The accession numbers of the synthases involved in the biosynthesis of the following products were as follows: saframycin (AAC44129), lyngbyatoxin (AAT12283), myxalamid (AAK57184), myxochelin (AAG31130), gramicidin (Q70LM4), Lys2 (AAA34747), glycopeptidolipid (CAB55600), BT peptide (AAY29583), nostocyclopeptide (AA023334), and TPS (AAM78457). (C) MOE 2008.10-generated 2D ligands of the final four residues were used in reductase model docking; * represents the thioester group involved in the reduction reaction.