title: Giant plasmid-encoded polyketide synthases produce the macrolide toxin of Mycobacterium ulcerans.
abstract: Mycobacterium ulcerans (MU), an emerging human pathogen harbored by aquatic insects, is the causative agent of Buruli ulcer, a devastating skin disease rife throughout Central and West Africa. Mycolactone, an unusual macrolide with cytotoxic and immunosuppressive properties, is responsible for the massive s.c. tissue destruction seen in Buruli ulcer. Here, we show that MU contains a 174-kb plasmid, pMUM001, bearing a cluster of genes encoding giant polyketide synthases (PKSs), and polyketide-modifying enzymes, and demonstrate that these are necessary and sufficient for mycolactone synthesis. This is a previously uncharacterized example of plasmid-mediated virulence in a Mycobacterium, and the emergence of MU as a pathogen most likely reflects the acquisition of pMUM001 by horizontal transfer. The 12-membered core of mycolactone is produced by two giant, modular PKSs, MLSA1 (1.8 MDa) and MLSA2 (0.26 MDa), whereas its side chain is synthesized by MLSB (1.2 MDa), a third modular PKS highly related to MLSA1. There is an extreme level of sequence identity within the different domains of the MLS cluster (>97% amino acid identity), so much so that the 16 ketosynthase domains seem functionally identical. This is a finding of significant consequence for our understanding of polyketide biochemistry. Such detailed knowledge of mycolactone will further the investigation of its mode of action and the development of urgently needed therapeutic strategies to combat Buruli ulcer.
authors.affiliation: Unité de Génétique Moléculaire Bactérienne, Génopole, Institut Pasteur, 28 Rue du Docteur Roux, 75725 Paris Cedex 15, France.
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Stinear
authors.forename: Armand
authors.initials: A
authors.lastname: Mve-Obiang
authors.forename: Pamela L C
authors.initials: PL
authors.lastname: Small
authors.forename: Wafa
authors.initials: W
authors.lastname: Frigui
authors.forename: Melinda J
authors.initials: MJ
authors.lastname: Pryor
authors.forename: Roland
authors.initials: R
authors.lastname: Brosch
authors.forename: Grant A
authors.initials: GA
authors.lastname: Jenkin
authors.forename: Paul D R
authors.initials: PD
authors.lastname: Johnson
authors.forename: John K
authors.initials: JK
authors.lastname: Davies
authors.forename: Richard E
authors.initials: RE
authors.lastname: Lee
authors.forename: Sarojini
authors.initials: S
authors.lastname: Adusumilli
authors.forename: Thierry
authors.initials: T
authors.lastname: Garnier
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Haydock
authors.forename: Peter F
authors.initials: PF
authors.lastname: Leadlay
authors.forename: Stewart T
authors.initials: ST
authors.lastname: Cole
mesh_terms: D001427:Bacterial Toxins / Q000235:genetics*; D001483:Base Sequence; D004251:DNA Transposable Elements; D007783:Lactones / Q000378:metabolism*; D018942:Macrolides; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D019911:Mycobacterium ulcerans / Q000235:genetics* / Q000472:pathogenicity*; D010957:Plasmids
chemical_list: D001427:Bacterial Toxins; D004251:DNA Transposable Elements; D007783:Lactones; D018942:Macrolides; D009097:Multienzyme Complexes; C451488:mycolactone A; C451489:mycolactone B