Control of Unsaturation in De Novo Fatty Acid Biosynthesis by FabA
2022
Bartholow, Thomas G. | Sztain, Terra | Young, Megan A. | Lee, D John | Davis, Tony D. | Abagyan, Ruben | Burkart, Michael D.
Carrier protein-dependent biosynthesis provides a thiotemplated format for the production of natural products. Within these pathways, many reactions display exquisite substrate selectivity, a regulatory framework proposed to be controlled by protein–protein interactions (PPIs). In Escherichia coli, unsaturated fatty acids are generated within the de novo fatty acid synthase by a chain length-specific interaction between the acyl carrier protein AcpP and the isomerizing dehydratase FabA. To evaluate PPI-based control of reactivity, interactions of FabA with AcpP bearing multiple sequestered substrates were analyzed through NMR titration and guided high-resolution docking. Through a combination of quantitative binding constants, residue-specific perturbation analysis, and high-resolution docking, a model for substrate control via PPIs has been developed. The in silico results illuminate the mechanism of FabA substrate selectivity and provide a structural rationale with atomic detail. Helix III positioning in AcpP communicates sequestered chain length identity recognized by FabA, demonstrating a powerful strategy to regulate activity by allosteric control. These studies broadly illuminate carrier protein-dependent pathways and offer an important consideration for future inhibitor design and pathway engineering.
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