title: CmaE: a transferase shuttling aminoacyl groups between carrier protein domains in the coronamic acid biosynthetic pathway.
abstract: During the biosynthesis of the cyclopropyl amino acid coronamic acid from l-allo-Ile by the phytotoxic Pseudomonas syringae, the aminoacyl group covalently attached to the pantetheinyl arm of CmaA is shuttled to the HS-pantetheinyl arm of the protein CmaD by the aminoacyltransferase CmaE. CmaE will only recognize deacylated CmaA for initial complexation. The aminoacyl group becomes covalently attached to the active site Cys of CmaE and can then be transferred out to the holo pantetheinylated form of CmaD. Both l-Val/l-[14C]Val exchange studies and MALDI-TOF support a reversible shuttling process. Aminoacylated-S-CmaE will transfer the l-Val moiety to the HS-pantetheinyl arm of other T domains, including CytC2, BarA, and ArfA C2-A2-T2 but not to free HS-pantetheine. CmaD could be loaded with other amino acids, for example, l-Leu and l-Thr, by the action of heterologous donor T domains containing alternative aminoacyl groups. Additionally, CmaE is able to accept l-Phe as a substrate when presented on CmaD and is able to load this aminoacyl moiety onto heterologous T domains, expanding the potential for CmaE to be used as a tool for generating chemical diversity within an NRPS assembly line.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Strieter
authors.forename: Frédéric H
authors.initials: FH
authors.lastname: Vaillancourt
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000096:biosynthesis*; D049148:Aminoacylation; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D053898:Biosynthetic Pathways; D006639:Histidine / Q000737:chemistry; D007532:Isoleucine / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000737:chemistry; D017434:Protein Structure, Tertiary; D044224:Pseudomonas syringae / Q000201:enzymology; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D007532:Isoleucine; D010649:Phenylalanine; D006639:Histidine; C043950:1-amino-2-ethylcyclopropane-1-carboxylic acid