mupirocin and pelargonic-acid

Mupirocin is a clinically important antibiotic produced by Pseudomonas fluorescens NCIMB 10586 that is assembled by a complex trans-AT polyketide synthase. The polyketide fragment, monic acid, is esterified by a 9-hydroxynonanoic acid (9HN) side chain which is essential for biological activity. The ester side chain assembly is initialised from a 3-hydroxypropionate (3HP) starter unit attached to the acyl carrier protein (ACP) MacpD, but the fate of this species is unknown. Herein we report the application of NMR spectroscopy, mass spectrometry, chemical probes and in vitro assays to establish the remaining steps of 9HN biosynthesis. These investigations reveal a complex interplay between a novel iterative or "stuttering" KS-AT didomain (MmpF), the multidomain module MmpB and multiple ACPs. This work has important implications for understanding the late-stage biosynthetic steps of mupirocin and will be important for future engineering of related trans-AT biosynthetic pathways (e.g. thiomarinol).

Topics: Acyl Carrier Protein; Anti-Bacterial Agents; Mupirocin; Polyketide Synthases

An analogue of isoleucyl-adenylate (Ile-AMS) potently inhibits the isoleucyl-tRNA synthetases (IleRSs) from the three primary kingdoms, whereas the antibiotic mupirocin inhibits only the eubacterial and archaeal IleRSs, but not the eukaryotic enzymes, and therefore is clinically used against methicillin-resistant Staphylococcus aureus. We determined the crystal structures of the IleRS from the thermophilic eubacterium, Thermus thermophilus, in complexes with Ile-AMS and mupirocin at 3.0- and 2.5-A resolutions, respectively. A structural comparison of the IleRS.Ile-AMS complex with the adenylate complexes of other aminoacyl-tRNA synthetases revealed the common recognition mode of aminoacyl-adenylate by the class I aminoacyl-tRNA synthetases. The Ile-AMS and mupirocin, which have significantly different chemical structures, are recognized by many of the same amino acid residues of the IleRS, suggesting that the antibiotic inhibits the enzymatic activity by blocking the binding site of the high energy intermediate, Ile-AMP. In contrast, the two amino acid residues that concomitantly recognize Ile-AMS and mupirocin are different between the eubacterial/archaeal IleRSs and the eukaryotic IleRSs. Mutagenic analyses revealed that the replacement of the two residues significantly changed the sensitivity to mupirocin.

Topics: Adenosine Monophosphate; Amino Acid Sequence; Amino Acids; Amino Acyl-tRNA Synthetases; Anti-Bacterial Agents; Binding Sites; Crystallography, X-Ray; Fatty Acids; Inhibitory Concentration 50; Isoleucine; Isoleucine-tRNA Ligase; Kinetics; Models, Chemical; Models, Molecular; Molecular Sequence Data; Mupirocin; Mutagenesis, Site-Directed; Phosphates; Protein Conformation; Protein Structure, Secondary; Sequence Homology, Amino Acid; Staphylococcus aureus; Thermus thermophilus