Off-loading Dieckmann cyclase, NcmC, that installs the tetramate head group in nocamycin, a hybrid polyketide/nonribosomalpeptide natural product. A conserved thioesterase-like scaffold has been adapted to perform a new chemical reaction: heterocyclization. The catalytic triad for the cyclization reaction consists of Cys89, Asp116, and His254
(Below N is a link to NCBI taxonomic web page and E link to ESTHER at designed phylum.) > cellular organisms: NE > Bacteria: NE > Terrabacteria group: NE > Actinobacteria [phylum]: NE > Actinobacteria [class]: NE > Pseudonocardiales: NE > Pseudonocardiaceae: NE > Saccharothrix: NE > Saccharothrix syringae: NE
LegendThis sequence has been compared to family alignement (MSA) red => minority aminoacid blue => majority aminoacid color intensity => conservation rate title => sequence position(MSA position)aminoacid rate Catalytic site Catalytic site in the MSA MTAPRAWRPIAGGPPAGPLVLAVDFAATGRPEAAFADLVARLDPGTEVWE SLQPPLGTETGMVAEDYVTRWEEEVRASGRRIGAVLGFCAGSAFAGELAV RLARSQPRSPRLVVFDPESPTTSTLYYQFRKVVESLAGVLGEQAAREALA EGTAAADRIGDVEGLGAELVRVFTAAGRAACAAADLDDEFADELTATYRS FVSYLVAAAAVDHVKCWSGAVAVSSATPTSGLNPLDPAARAALVERELTF DVHHADLLRDPGVARAVARLLA
Reference
Title: Structural Basis for Enzymatic Off-Loading of Hybrid Polyketides by Dieckmann Condensation Cogan DP, Ly J, Nair SK Ref: ACS Chemical Biology, 15:2783, 2020 : PubMed
While several bioactive natural products that contain tetramate or pyridone heterocycles have been described, information on the enzymology underpinning these functionalities has been limited. Here we biochemically characterize an off-loading Dieckmann cyclase, NcmC, that installs the tetramate headgroup in nocamycin, a hybrid polyketide/nonribosomal peptide natural product. Crystal structures of the enzyme (1.6 A) and its covalent complex with the epoxide cerulenin (1.6 A) guide additional structure-based mutagenesis and product-profile analyses. Our results offer mechanistic insights into how the conserved thioesterase-like scaffold has been adapted to perform a new chemical reaction, namely, heterocyclization. Additional bioinformatics combined with docking and modeling identifies likely candidates for heterocycle formation in underexplored gene clusters and uncovers a modular basis of substrate recognition by the two subdomains of these Dieckmann cyclases.
Saccharothrix syringae. NcmC
