title: Two polyketide-synthase-associated acyltransferases are required for sulfolipid biosynthesis in Mycobacterium tuberculosis.
abstract: The methyl-branched fatty acyl components of sulfolipid-I (SL-I), a major glycolipid of the human pathogen Mycobacterium tuberculosis, are synthesized by the polyketide synthase Pks2. Rv3824c (papA1), located downstream of pks2, encodes a protein that belongs to a subfamily of acyltransferases associated with mycobacterial polyketide synthases [polyketide synthase-associated proteins (PAPs)]. The presence of a conserved acyltransferase motif (HX(3)DX(14)Y) suggested a role for PapA1 in acylation of sulfated trehalose to form SL-I. Targeted deletion of the H37Rv papA1 resulted in loss of SL-I, demonstrating its role in mycobacterial sulfolipid biosynthesis. Furthermore, SL-I synthesis was restored in the mutant strain following complementation with papA1, but not with mutant alleles of papA1 containing alterations of key residues in the acyltransferase motif, confirming that PapA1 was an acyltransferase. While other M. tuberculosis pks clusters are associated with a single PAP-encoding gene, it was demonstrated that another open reading frame, Rv3820c (papA2), located 5.8 kb downstream of papA1 is also an acyltransferase gene involved in SL-I biosynthesis: deletion of papA2 abolished SL-I production. The absence of any partially acylated intermediates in either null mutant indicated that both PapA1 and PapA2 were required for all acylation steps of SL-I assembly.
authors.affiliation: Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
authors.forename: Kiranmai
authors.initials: K
authors.lastname: Bhatt
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Sudagar S
authors.initials: SS
authors.lastname: Gurcha
authors.affiliation: Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
authors.forename: Apoorva
authors.initials: A
authors.lastname: Bhatt
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
authors.affiliation: Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
authors.forename: William R
authors.initials: WR
authors.lastname: Jacobs
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006017:Glycolipids / Q000096:biosynthesis*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D048630:Polyketide Synthases / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors
chemical_list: D001426:Bacterial Proteins; D006017:Glycolipids; D037521:Virulence Factors; C009355:sulfolipid I; D048630:Polyketide Synthases; D000217:Acyltransferases