7FEV

Crystal structure of Old Yellow Enzyme6 (OYE6)

Summary for 7FEV

• Entry DOI: 10.2210/pdb7fev/pdb
• Descriptor: FMN binding, FLAVIN MONONUCLEOTIDE (3 entities in total)
• Functional Keywords: flavoenzyme, ascochyta rabiei, fmn-binding, fungal oyes, oxidoreductase
• Biological source: Ascochyta rabiei
• Total number of polymer chains: 1
• Total formula weight: 49636.59

Authors

Singh, Y.,Sharma, R.,Mishra, M.,Verma, P.K.,Saxena, A.K. (deposition date: 2021-07-21, release date: 2022-04-27, Last modification date: 2023-11-29)

Primary citation

Singh, Y.,Sharma, R.,Mishra, M.,Verma, P.K.,Saxena, A.K.
Crystal structure of ArOYE6 reveals a novel C-terminal helical extension and mechanistic insights into the distinct class III OYEs from pathogenic fungi.
Febs J., 289:5531-5550, 2022

PubMed Abstract: Old yellow enzymes (OYEs) play a critical role in antioxidation, detoxification and ergot alkaloid biosynthesis processes in various organisms. The yeast- and bacteria-like OYEs have been structurally characterized earlier, however, filamentous fungal pathogens possess a novel OYE class, that is, class III, whose biochemical and structural intricacies remain unexplored to date. Here, we present the 1.6 Å X-ray structure of a class III member, OYE 6 from necrotrophic fungus Ascochyta rabiei (ArOYE6), in flavin mononucleotide (FMN)-bound form (PDB ID-7FEV) and provide mechanistic insights into their catalytic capability. We demonstrate that ArOYE6 exists as a monomer in solution, forms (β/α) barrel structure harbouring non-covalently bound FMN at cofactor binding site, and utilizes reduced nicotinamide adenine dinucleotide phosphate as its preferred reductant. The large hydrophobic cavity situated above FMN, specifically accommodates 12-oxo-phytodienoic acid and N-ethylmaleimide substrates as observed in ArOYE6-FMN-substrate ternary complex models. Site-directed mutations in the conserved catalytic (His196, His199 and Tyr201) and FMN-binding (Lys249 and Arg348) residues render the enzyme inactive. Intriguingly, the ArOYE6 structure contains a novel C-terminus (369-445 residues) made of three α-helices, which stabilizes the FMN binding pocket as its mutation/truncation lead to complete loss of FMN binding. Moreover, the loss of the extended C-terminus does not alter the monomeric nature of ArOYE6. In this study, for the first time, we provide the structural and biochemical insights for a fungi-specific class III OYE homologue and dissect the oxidoreductase mechanism. Our findings hold broad biological significance during host-fungus interactions owing to the conservation of this class among pathogenic fungi, and would have potential implications in the pharmacochemical industry.

PubMed: 35313092
DOI: 10.1111/febs.16445

Experimental method

X-RAY DIFFRACTION (1.594 Å)