Pseudomonas syringae pv. glycinea PG4180 produces the chlorosis-inducing phytotoxin coronatine (COR), which consists of a polyketide component, coronafacic acid (CFA), ligated by an amide bond to coronamic acid (CMA), an ethylcyclopropyl amino-acid derived from isoleucine. We report the nucleotide sequence of a 2.37-kb region containing the coronafacate ligase-encoding gene (cfl) which is required for the amide linkage of CFA and CMA. The transcription start point for cfl was identified, and the Cfl protein was overproduced from the T7lac promoter in Escherichia coli. The deduced amino-acid sequence of Cfl showed homology to a variety of adenylate-forming enzymes which bind and hydrolyze ATP in order to activate their substrates for further ligation.