Biochemical interactions between the Atm1-like transporter from Novosphingobium aromaticivorans and heavy metals

• Published in: Archives of biochemistry and biophysics 2023-08, Vol.744, p.109696-109696, Article 109696
• Main Authors: Rottet, Sarah, Iqbal, Shagufta, Xifaras, Rachel, Singer, Michael T., Scott, Colin, Deplazes, Evelyne, Callaghan, Richard
• Format: Article
• Language: English
• Subjects: ATP-Binding cassette transporter; Glutathione; Heavy metal; Iron transport; Iron-porphyrin; Membrane transport; Molecular docking; Reconstitution; SMALP; Styrene-maleic acid
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2023.109696

Novosphingobium aromaticivorans has the ability to survive in harsh environments by virtue of its suite of iron-containing oxygenases that biodegrade an astonishing array of aromatic compounds. It is also resistant to heavy metals through Atm1, an ATP-binding cassette protein that mediates active efflux of heavy metals conjugated to glutathione. However, Atm1 orthologues in higher organisms have been implicated in the intracellular transport of organic iron complexes. Our hypothesis suggests that the ability of Atm1 to remove heavy metals is related to the need for regulated iron handling in N. aromaticivorans to support high oxygenase activity. Here we provide the first data demonstrating a direct interaction between an iron-porphyrin compound (hemin) and NaAtm1. Hemin displayed considerably higher binding affinity and lower EC50 to stimulate ATP hydrolysis by Atm1 than Ag-GSH, GSSG or GSH, established substrates of the transporter. Co-incubation of NaAtm1 and hemin with Ag-GSH in ATPase assays revealed a non-competitive interaction, indicating distinct binding sites on NaAtm1 and this property was reinforced using molecular docking analysis. Our data suggests that NaAtm1 has considerable versatility in transporting organic conjugates of metals and that this versatility enables it to play roles in detoxification processes for toxic metals and in homeostasis of iron. The ability to play these distinct roles is enabled by the plasticity of the substrate binding site within the central cavity of NaAtm1. [Display omitted] •N. aromaticivorans can survive in environments polluted with heavy metals.•Heavy metals are extruded from N. aromaticivorans by the ABC protein Atm1.•Atm1 binds and transports glutathione conjugates of heavy metals.•Orthologues of Atm1 in higher species are thought to mediate iron transport.•Hemin can bind to Atm1 from N. aromaticivorans and stimulate its ATPase activity.