title: An Activator of an Adenylation Domain Revealed by Activity but Not Sequence Homology.
abstract: Nonribosomal peptide synthetases (NRPSs), which are responsible for synthesizing many medicinally important natural products, frequently use adenylation domain activators (ADAs) to promote substrate loading. Although ADAs are usually MbtH-like proteins (MLPs), a new type of ADA appears to promote an NRPS-dependent incorporation of a dihydropyrrole unit into sibiromycin. The adenylation and thiolation didomain of the NRPS SibD catalyzes the adenylation of a limited number of amino acids including l-Tyr, the precursor in dihydropyrrole biosynthesis, as determined by a standard radioactivity exchange assay. LC-MS/MS analysis confirmed loading of l-Tyr onto the thiolation domain. SibB, a small protein with no prior functional assignment or sequence homology to MLPs, was found to promote the exchange activity. MLPs from bacteria expressing homologous biosynthetic pathways were unable to replace this function of SibB. The discovery of this new type of ADA demonstrates the importance of searching beyond the conventional MLP standard for proteins affecting NRPS activity.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA. ssaha1@umd.edu.
authors.forename: Shalini
authors.initials: S
authors.lastname: Saha
authors.affiliation: Department of Chemistry, Johns Hopkins University, 3400 N. Charles St, Baltimore, MD, 21218, USA. rokita@jhu.edu.
authors.forename: Steven E
authors.identifier: 0000-0002-2292-2917
authors.initials: SE
authors.lastname: Rokita
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D055162:Biocatalysis; D009169:Mycobacterium tuberculosis; D010453:Peptide Synthases / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase
keywords: MbtH; adenylation domain activators; biosynthesis; natural products; nonribosomal peptide synthetases