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Journal Articles Physical Chemistry Chemical Physics Year : 2017

Ultrafast photochemistry of the bc 1 complex

Marten H. Vos
Ursula Liebl


We present a full investigation of ultrafast light-induced events in the membraneous cytochrome bc1 complex by transient absorption spectroscopy. This energy-transducing complex harbors four redox-active components per monomer: heme c1, two 6-coordinate b-hemes and a [2Fe-2S] cluster. Using excitation of these components in different ratios under various excitation conditions, probing in the full visible range and under three well-defined redox conditions, we demonstrate that for all ferrous hemes of the complex photodissociation of axial ligands takes place and that they rebind in 5-7 ps, as in other 6-coordinate heme proteins, including cytoglobin, which is included as a reference in this study. By contrast, the signals are not consistent with photooxidation of the b hemes. This conclusion contrasts with a recent assessment based on a more limited data set. The binding kinetics of internal and external ligands are indicative of a rigid heme environment, consistent with the electron transfer function. We also report, for the first time, photoactivity of the very weakly absorbing iron-sulfur center. This yields the unexpected perspective of studying photochemistry, initiated by excitation of iron-sulfur clusters, in a range of protein complexes.

Dates and versions

hal-01662320 , version 1 (11-05-2023)



Marten H. Vos, Brandon J. Reeder, Fevzi Daldal, Ursula Liebl. Ultrafast photochemistry of the bc 1 complex. Physical Chemistry Chemical Physics, 2017, 19 (9), pp.6807-6813. ⟨10.1039/C7CP00193B⟩. ⟨hal-01662320⟩
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