Structure and biosynthesis model of syringolin A. A. Structure of syringolin A. Amino acid constituents are delimited by bars. Val, valine. B. Genomic region of Pss B301D-R containing the sylA-sylE genes. Boxes above and below the line denote ORFs on the top and the bottom strand, respectively. Arrows indicate restriction sites used for cloning of the gene cluster into the cosmid pPL3syl. The sylA, sylB, and sylE genes encode a LuxR-type transcription activator, a rhizobitoxin desaturase-like protein thought to desaturate the lysine residue, and an efflux transporter, respectively . The sylC gene encodes an NRPS module, while sylD codes for two NRPS modules and one PKS module  C. Biosynthesis model of the tripeptide part of syringolin A. The open boxes represent domains in modules of the syringolin A synthetase labeled with C, condensation domain; A, adenylation domain; PC, peptide carrier protein; KS, ketoacyl synthase; AT, acyl transferase; DH, dehydratase; KR, ketoreductase; AC, acyl carrier protein; TE, thioesterase. The A domains of the NRPS modules are thought to activate valine (NRPS mod1), lysine (NRPS mod2), and valine (NRPS mod3) . The question mark indicates the unexplained synthesis and attachment of this group. The figures are adapted from .
Ramel et al. BMC Biochemistry 2009 10:26 doi:10.1186/1471-2091-10-26