The sypA, sypS, and sypC synthetase genes encode twenty-two modules involved in the nonribosomal peptide synthesis of syringopeptin by Pseudomonas syringae pv. syringae B301D.
Syringopeptin is a necrosis-inducing phytotoxin, composed of 22 amino acids attached to a 3-hydroxy fatty acid tail. Syringopeptin, produced by Pseudomonas syringae pv. syringae, functions as a virulence determinant in the plant-pathogen interaction. A 73,800-bp DNA region was sequenced, and analysis identified three large open reading frames, sypA, sypB, and sypC, that are 16.1, 16.3, and 40.6 kb in size. Sequence analysis of the putative SypA, SypB, and SypC sequences determined that they are homologous to peptide synthetases, containing five, five, and twelve amino acid activation modules, respectively. Each module exhibited characteristic domains for condensation, aminoacyl adenylation, and thiolation. Within the aminoacyl adenylation domain is a region responsible for substrate specificity. Phylogenetic analysis of the substrate-binding pockets resulted in clustering of the 22 syringopeptin modules into nine groups. This clustering reflects the substrate amino acids predicted to be recognized by each of the respective modules based on placement of the syringopeptin NRPS (nonribosomal peptide synthetase) system in the linear (type A) group. Finally, SypC contains two C-terminal thioesterase domains predicted to catalyze the release of syringopeptin from the synthetase and peptide cyclization to form the lactone ring. The syringopeptin synthetases, which carry 22 NRPS modules, represent the largest linear NRPS system described for a prokaryote.
Department of Plant Pathology, Washington State University, Pullman, Washington 99164-6430, USA.
Brenda K
BK
Scholz-Schroeder
Jonathan D
JD
Soule
Dennis C
DC
Gross
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000145:classification / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D008074:Lipoproteins / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D010453:Peptide Synthases / Q000235:genetics*; D010456:Peptides, Cyclic / Q000096:biosynthesis* / Q000235:genetics; D010802:Phylogeny; D010957:Plasmids; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics*; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D001426:Bacterial Proteins; D008074:Lipoproteins; D010456:Peptides, Cyclic; D010453:Peptide Synthases