title: Generation of D amino acid residues in assembly of arthrofactin by dual condensation/epimerization domains.
abstract: The first 6 residues of the biosurfactant lipopeptidolactone arthrofactin have the D configuration, yet none of the 11 modules of the nonribosomal peptide synthetase assembly line have epimerization domains. We show that the two-module ArfA subunit and the first module of the ArfB subunit, which act in tandem to produce the N-acyl-D-Leu1-D-Asp2-D-Thr3-S-protein intermediate, activate the L amino acids and epimerize them as the aminoacyl-S-pantetheinyl T domain intermediates before the next downstream condensation. The condensation (C) domains are shown to have (D)C(L) chirality in peptide bond formation. The upstream aminoacyl/peptidyl moiety is epimerized before condensation only when the condensation domains are simultaneously presented with the L-aminoacyl-S-pantetheinyl acceptor. These (D)C(L) catalysts are dual function condensation/epimerization domains that can be predicted by bioinformatics analysis to be responsible for incorporation of all D residues in arthrofactin and of D residues in syringomycin, syringopeptin, and ramoplanin synthetases.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Balibar
authors.forename: Frédéric H
authors.initials: FH
authors.lastname: Vaillancourt
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D000107:Acetylation; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry* / Q000378:metabolism*; D003001:Cloning, Molecular; D015870:Gene Expression; D008025:Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055666:Lipopeptides; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010456:Peptides, Cyclic / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics; D010802:Phylogeny; D011549:Pseudomonas / Q000235:genetics; D019998:Racemases and Epimerases / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D055666:Lipopeptides; D010456:Peptides, Cyclic; C083714:arthrofactin; D000255:Adenosine Triphosphate; D019998:Racemases and Epimerases; D008025:Ligases