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Structural basis of carnitine monooxygenase CntA substrate specificity, inhibition and inter-subunit electron transfer

DOI: 10.1074/jbc.RA120.016019 DOI Help

Authors: Mussa Quareshy (University of Warwick) , Muralidharan Shanmugam (University of Manchester) , Eleanor Townsend (University of Warwick) , Eleanor Jameson (University of Warwick) , Timothy D. H. Bugg (University of Warwick) , Alexander D. Cameron (University of Warwick) , Yin Chen (University of Warwick)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 19880

Abstract: Microbial metabolism of carnitine to trimethylamine (TMA) in the gut can accelerate atherosclerosis and heart disease and these TMA-producing enzymes are therefore important drug targets. Here, we report the first structures of the carnitine oxygenase CntA, an enzyme of the Rieske oxygenase family. CntA exists in a head-to-tail a3 trimeric structure. The two functional domains (the Rieske and the catalytic mononuclear iron domains) are located > 40 Å apart in the same monomer but adjacent in two neighbouring monomers. Structural determination of CntA and subsequent electron paramagnetic resonance measurements uncover the molecular basis of the so-called bridging glutamate (E205) residue in inter-subunit electron transfer. The structures of the substrate-bound CntA help to define the substrate pocket. Importantly, a tyrosine residue (Y203) is essential for ligand recognition through a π-cation interaction with the quaternary ammonium group. This interaction between an aromatic residue and quaternary amine substrates allows us to delineate a subgroup of Rieske oxygenases (group V) from the prototype ring-hydroxylating Rieske oxygenases involved in bioremediation of aromatic pollutants in the environment. Furthermore, we report the discovery of the first known CntA inhibitors and solve the structure of CntA in complex with the inhibitor, demonstrating the pivotal role of Y203 through a π-π stacking interaction with the inhibitor. Our study provides the structural and molecular basis for future discovery of drugs targeting this TMA-producing enzyme in human gut.

Journal Keywords: gut microbiota; inhibitor; carnitine oxygenase; CntA; microbiology; enzyme structure; microbiome; cardiovascular disease; crystal structure

Subject Areas: Biology and Bio-materials, Chemistry, Medicine

Instruments: I04-Macromolecular Crystallography , I24-Microfocus Macromolecular Crystallography