bims-resufa 2019-11-17 papers

Issue of 2019–11–17
two papers selected by
Vera Strogolova, Marquette University

FEBS Lett. 2019 Nov 14.

Proton transfer in uncoupled variants of cytochrome c oxidase.

Jóhanna Vilhjálmsdóttir, Ingrid Albertsson, Margareta R A Blomberg, Pia Ädelroth, Peter Brzezinski.

Cytochrome c oxidase is a membrane-bound redox-driven proton pump, which harbors two proton-transfer pathways, D and K, used at different stages of the reaction cycle. Here, we address the question if a D pathway with a modified energy landscape for proton transfer could take over the role of the K pathway when the latter is blocked by a mutation. Our data indicate that structural alterations near the entrance of the D pathway modulate energy barriers that influence proton transfer to the proton-loading site. The data also suggest that during reduction of the catalytic site, its protonation has to occur via the K pathway and that this proton transfer to the catalytic site cannot take place through the D pathway.

Keywords: cytochrome aa3; electron transfer; mechanism; membrane protein; proton pumping; proton transfer

DOI: https://doi.org/10.1002/1873-3468.13679

Biophys Chem. 2019 Nov 02. pii: S0301-4622(19)30349-7. [Epub ahead of print]256 106276

Explaining leak states in the proton pump of heme-copper oxidases observed in single-molecule experiments.

Luigi Leonardo Palese.

Heme-copper oxidases couple the exergonic oxygen reduction with the endergonic proton translocation. Redox-linked structural changes have been localized in deeply buried regions of the protein, near the low-potential heme. How these movements can modulate distant gating events along the intramolecular proton path, where the entry (exit) of pumped proton occurs, is a major concern for the proton pump models. Generally, these models associate, more or less directly, all translocation events with redox transitions. Although they can account for many phenomenological aspects of the pump, evidences from single-molecules experiments about leak states of the pump represent a formidable challenge. Disconnecting the redox-linked pKa shifts of the proton loading site from the external barriers, we obtain a simple stochastic mechanism which behaves similarly to the real enzyme, able to reverse the flow of the proton transfer.

Keywords: Discrete Markov model; Heme-copper oxidase; Proton pump; Reactive oxygen species; Single-molecule; Stochastic pump

DOI: https://doi.org/10.1016/j.bpc.2019.106276