Structural and functional investigation of the periplasmic arsenate-binding protein ArrX from Chrysiogenes arsenatis

DOI: 10.1021/acs.biochem.0c00555

Authors: Nilakhi Poddar (The University of Melbourne) , Consuelo Badilla (University College London) , Shadi Maghool (The University of Melbourne) , Thomas H. Osborne (University College London) , Joanne M. Santini (University College London) , Megan J. Maher (The University of Melbourn; La Trobe University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemistry

State: Published (Approved)
Published: February 2021

Abstract: The anaerobic bacterium Chrysiogenes arsenatis respires using the oxyanion arsenate (AsO43–) as the terminal electron acceptor, where it is reduced to arsenite (AsO33–) while concomitantly oxidizing various organic (e.g., acetate) electron donors. This respiratory activity is catalyzed in the periplasm of the bacterium by the enzyme arsenate reductase (Arr), with expression of the enzyme controlled by a sensor histidine kinase (ArrS) and a periplasmic-binding protein (PBP), ArrX. Here, we report for the first time, the molecular structure of ArrX in the absence and presence of bound ligand arsenate. Comparison of the ligand-bound structure of ArrX with other PBPs shows a high level of conservation of critical residues for ligand binding by these proteins; however, this suite of PBPs shows different structural alterations upon ligand binding. For ArrX and its homologue AioX (from Rhizobium sp. str. NT-26), which specifically binds arsenite, the structures of the substrate-binding sites in the vicinity of a conserved and critical cysteine residue contribute to the discrimination of binding for these chemically similar ligands.

Journal Keywords: Chemical structure; Anions; Peptides and proteins; Crystal structure; Ions

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: I04-Macromolecular Crystallography

Other Facilities: MX2 beamline at Australian Synchrotron

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