title: Structural insights into biosynthesis of resorcinolic lipids by a type III polyketide synthase in Neurospora crassa.
abstract: Microbial type III polyketide synthases (PKSs) have revealed remarkable mechanistic as well as functional versatility. Recently, a type III PKS homolog from Azotobacter has been implicated in the biosynthesis of resorcinolic lipids, thus adding a new functional significance to this class of proteins. Here, we report the structural and mutational investigations of a novel type III PKS protein from Neurospora crassa involved in the biosynthesis of resorcinolic metabolites by utilizing long chain fatty acyl-CoAs. The structure revealed a long hydrophobic tunnel responsible for its fatty acyl chain length specificity resembling that of PKS18, a mycobacterial type III PKS. Structure-based mutational studies to block the tunnel not only altered the fatty acyl chain specificity but also resulted in change of cyclization pattern affecting the product profile. This first structural characterization of a resorcinolic lipid synthase provides insights into the coordinated functioning of cyclization and a substrate-binding pocket, which shows mechanistic intricacy underlying type III PKS catalysis.
authors.affiliation: Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
authors.forename: Aneesh
authors.initials: A
authors.lastname: Goyal
authors.forename: Priti
authors.initials: P
authors.lastname: Saxena
authors.forename: Ataur
authors.initials: A
authors.lastname: Rahman
authors.forename: Parmit Kumar
authors.initials: PK
authors.lastname: Singh
authors.forename: Durgadas P
authors.initials: DP
authors.lastname: Kasbekar
authors.forename: Rajesh S
authors.initials: RS
authors.lastname: Gokhale
authors.forename: Rajan
authors.initials: R
authors.lastname: Sankaranarayanan
mesh_terms: D001395:Azotobacter / Q000378:metabolism; D001671:Biochemistry / Q000379:methods; D002384:Catalysis; D019295:Computational Biology; D018360:Crystallography, X-Ray / Q000379:methods; D004252:DNA Mutational Analysis; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D007700:Kinetics; D008055:Lipids / Q000737:chemistry*; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D009492:Neurospora crassa / Q000201:enzymology*; D010802:Phylogeny; D048630:Polyketide Synthases / Q000737:chemistry*
chemical_list: D008055:Lipids; D048630:Polyketide Synthases