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Analysis of SEC-SAXS data via EFA deconvolution and Scatter

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A structural model of PpoA derived from SAXS-analysis-implications for substrate conversion.

Christian Koch¹, Giancarlo Tria, Alistair J Fielding

¹Georg-August-University, Albrecht-von-Haller-Institute, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, D-37077 Goettingen, Germany.

Biochimica Et Biophysica Acta

|June 26, 2013

Summary

This study reveals the trimeric structure of Aspergillus nidulans PpoA, a bifunctional enzyme crucial for oxylipin biosynthesis in fungi. The research clarifies the enzyme's spatial organization and identifies key residues influencing its catalytic activity.

Keywords:

AOS Cytochrome P450 D(max)DEER DES DOX DiHODE DiHOME Dioxygenase Double electron–electron resonance EPR Et(2)O H(P)ODE HPL KODE KOME LOX MALDI-TOF MW Oxylipin PGHS PGIS Ppo Psi-factor producing oxygenase R(g)SAXS Small-angle X-ray scattering TXAS V(p)allene oxide synthase diethyl ether dihydroxy linoleic acid dihydroxy oleic acid dioxygenase divinyl ether synthase double electron–electron resonance electron paramagnetic resonance hydro(pero)xy linoleic acid hydroperoxide lyase lipoxygenase matrix-assisted laser desorption/ionization-time of flight maximal particle dimension molecular weight oxo-linoleic acid oxo-oleic acid particle volume precocious sexual inducer prostacyclin synthase prostaglandin endoperoxide synthase psi psi-factor producing oxygenase radius of gyration small-angle X-ray scattering thromboxane synthase

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Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092

Biochemical and Structural Characterization of the Carbohydrate Transport Substrate-binding-protein SP0092

Published on: October 2, 2017

Area of Science:

Biochemistry
Molecular Biology
Mycology

Background:

Oxylipins are vital signaling molecules in plants and mammals, synthesized via dioxygenation and isomerization of hydroperoxy fatty acids.
These processes are typically catalyzed by separate dioxygenase and cytochrome P450 enzymes.
In ascomycetes, bifunctional enzymes named Psi-factor producing oxygenases (Ppo) can combine both activities.

Purpose of the Study:

To investigate the spatial organization of the bifunctional PpoA enzyme from Aspergillus nidulans.
To elucidate the structural basis for the combined dioxygenase and P450 activities in fungal oxylipin biosynthesis.
To identify specific amino acid residues involved in enzyme function and specificity.

Main Methods:

Small-angle X-ray scattering (SAXS) to determine the overall enzyme shape.
Template-based structure prediction for individual enzyme domains.
Docking of predicted domain structures into the SAXS-derived enzyme envelope.
Electron Paramagnetic Resonance (EPR) spectroscopy for distance measurements and radical site identification.

Main Results:

PpoA exhibits a relatively flat trimeric structure.
SAXS data and EPR measurements confirmed the trimeric organization and identified Tyr374 as the radical site in the dioxygenase domain.
Atomic structures of single domains were successfully docked into the SAXS envelope.
Two phenylalanine residues in the cytochrome P450 domain were identified as modulators of hydroperoxy fatty acid rearrangement specificity.

Conclusions:

The study provides a low-resolution structure of the bifunctional PpoA enzyme, revealing its trimeric assembly.
Structural insights support the dual catalytic role of PpoA in fungal oxylipin synthesis.
Key residues influencing enzyme activity and substrate specificity have been identified, paving the way for further functional studies.