title: Dissecting the mechanism and assembly of a complex virulence mycobacterial lipid.
abstract: Mycobacterium tuberculosis cell envelope is a treasure house of biologically active lipids of fascinating molecular architecture. Although genetic studies have alluded to an array of genes in biosynthesis of complex lipids, their mechanistic, structural, and biochemical principles have not been investigated. Here, we have dissected the molecular logic underlying the biosynthesis of a virulence lipid phthiocerol dimycocerosate (PDIM). Cell-free reconstitution studies demonstrate that polyketide synthases, which are usually involved in the biosynthesis of secondary metabolites, are responsible for generating complex lipids in mycobacteria. We show that PapA5 protein directly transfers the protein bound mycocerosic acid analogs on phthiocerol to catalyze the final esterification step. Based on precise identification of biological functions of proteins from Pps cluster, we have rationally produced a nonmethylated variant of mycocerosate esters. Apart from elucidating mechanisms that generate chemical heterogeneity with PDIMs, this study also presents an attractive approach to explore host-pathogen interactions by altering mycobacterial surface coat.
authors.affiliation: National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India.
authors.forename: Omita A
authors.initials: OA
authors.lastname: Trivedi
authors.forename: Pooja
authors.initials: P
authors.lastname: Arora
authors.forename: Archana
authors.initials: A
authors.lastname: Vats
authors.forename: Mohd Zeeshan
authors.initials: MZ
authors.lastname: Ansari
authors.forename: Rashmi
authors.initials: R
authors.lastname: Tickoo
authors.forename: Vijayalakshmi
authors.initials: V
authors.lastname: Sridharan
authors.forename: Debasisa
authors.initials: D
authors.lastname: Mohanty
authors.forename: Rajesh S
authors.initials: RS
authors.lastname: Gokhale
mesh_terms: D000942:Antigens, Bacterial / Q000737:chemistry*; D002384:Catalysis; D002474:Cell-Free System; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D004952:Esters / Q000737:chemistry; D005227:Fatty Acids / Q000737:chemistry; D007700:Kinetics; D008055:Lipids / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009161:Mycobacterium / Q000378:metabolism* / Q000472:pathogenicity; D009169:Mycobacterium tuberculosis; D048630:Polyketide Synthases / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012984:Software; D013997:Time Factors; D014774:Virulence
chemical_list: D000942:Antigens, Bacterial; D004952:Esters; D005227:Fatty Acids; D008055:Lipids; C032992:mycocerosic acid; C008901:phthiocerol dimycocerosate; D048630:Polyketide Synthases