Visualizing the movement of the amphipathic helix in the respiratory complex I using a nitrile infrared probe and SEIRAS

• Published in: FEBS letters Vol. 594; no. 3; pp. 491 - 496
• Main Authors: Santos Seica, Ana Filipa, Schimpf, Johannes, Friedrich, Thorsten, Hellwig, Petra
• Format: Journal Article
• Language: English
• Published: England Wiley 01-02-2020
• Subjects: Chemical Sciences; infrared nitrile labels; Other; respiratory complex I; SEIRAS; infrared nitrile labels; respiratory complex I; SEIRAS
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1002/1873-3468.13620

Conformational movements play an important role in enzyme catalysis. Respiratory complex I, an L‐shaped enzyme, connects electron transfer from NADH to ubiquinone in its peripheral arm with proton translocation through its membrane arm by a coupling mechanism still under debate. The amphipathic helix across the membrane arm represents a unique structural feature. Here, we demonstrate a new way to study conformational changes by introducing a small and highly flexible nitrile infrared (IR) label to this helix to visualize movement with surface‐enhanced IR absorption spectroscopy. We find that labeled residues K551CL and Y590CL move to a more hydrophobic environment upon NADH reduction of the enzyme, likely as a response to the reorganization of the antiporter‐like subunits in the membrane arm.