H2 -Fueled ATP Synthesis on an Electrode: Mimicking Cellular Respiration

Abstract

ATP, the molecule used by living organisms to supply energy to many different metabolic processes, is synthesized mostly by the ATPase synthase using a proton or sodium gradient generated across a lipid membrane. We present evidence that a modified electrode surface integrating a NiFeSe hydrogenase and a F1 F0 -ATPase in a lipid membrane can couple the electrochemical oxidation of H2 to the synthesis of ATP. This electrode-assisted conversion of H2 gas into ATP could serve to generate this biochemical fuel locally when required in biomedical devices or enzymatic synthesis of valuable products.

Keywords: bioelectrochemistry; biophysics; immobilization; membrane proteins; proton transport.

Figure 1

A) Representation of the supramolecular construction to synthesize ATP from enzymatic H₂ electroxidation. NiFeSe hydrogen‐ase (Hase) immobilized covalently on an Au electrode modified with a SAM of 4‐aminothiophenol and anchored to a PhBL through its lipid tail.16a The PhBL embeds F₁F₀‐ATPases. Protons (H⁺) produced from H₂ electroxidation are used to synthesize ATP from ADP and inorganic phosphate (Pi).

Figure 2

A–C) AFM topography images of A) the bare annealed gold surface, B) the Hase monolayer and C) the F1Fo ATPase reconstituted into the PhBL spread on the Hase monolayer. D) QCM monitoring of liposome (dashed line) and F₁F₀ proteoliposome (solid line) adsorption to a SiO₂ surface. Inset: AFM image of an F₁F₀‐ATPase‐containing PhBL. E–G) Three regions from AFM image in (D) used to estimate the average number of proteins protruding more than 5 nm (N=9 per 200×200 nm² ).

Figure 3

A) Cyclic voltammograms of the Hase/PhBL/ATPase‐modified electrode in 0.1 m phosphate buffer (pH 8.0) after Hase activation through H₂ incubation (solid line) or under N₂ before activation (dashed line). The star indicates the redox potential (150 mV vs. SCE) applied to drive ATP production. Scan rate=0.01 V s⁻¹. Temperature=30 °C. B) ATP synthesis from ADP and phosphate in 0.1 m phosphate buffer (pH 8.0) at 150 mV and under 1 atm H₂. ATP concentration in the bulk solution is shown as a function of time for Hase/PhBL/ATPase (black solid circles), PhBL/ATPase (gray solid circles), and Hase/PhBL (gray open circles) electrodes. Error bars=standard deviation of three measurements made from different electrode preparations.

Figure 4

A) Representation of the PhBL reconstituted with F₁F₀‐ATP synthase over an Au electrode. The ATP hydrolysis by F₁F₀ leads to proton pumping across the membrane, which results in a decrease of the pH of the aqueous compartment between the lipid membrane and the Au electrode surface. B) ATP hydrolysis monitored by phosphate production as a function of time for a F₁F₀‐proteoliposome‐modified electrode (black circles) and for a bare liposome‐modified electrode (gray circles). The initial ATP concentration was 150 µm and the temperature was 37 °C. C) The simultaneous proton pumping activity of F₁F₀‐ATP synthase was monitored over time by differential pulse voltammetry (inset). The oxidation peak potential of the SAM on Au is shown as a function of time after ATP hydrolysis started. Error bars=standard deviation of two independent measurements.