Ion pumps

Cytochrome c oxidase (CytcO) is the last enzyme of the electron transport chain, but how the electrochemical membrane potential affects CytcO is unclear. Here the authors show that proton uptake to the catalytic site of CytcO and presumably proton translocation was impaired by the potential, but electron transfer was not affected.

Proton pumps that are driven by light to pump protons out of the cell are involved in the conversion of sunlight into proton motive force; pumps to drive protons in the other direction have been engineered. Here, the authors report the identification and characterisation of a naturally occurring inward-driven protein pump.

Mep2 proteins are tightly regulated fungal ammonium transporters. Here, the authors report the crystal structures of closed states of Mep2 proteins and propose a model for their regulation by comparing them with the open ammonium transporters of bacteria.

The Na⁺,K⁺-ATPase moves three Na⁺ ions out of the cell and transfers two K⁺ ions in the opposite direction. Here the authors use X-ray crystallography to look at the substitution of two bound K⁺with those in the medium and show that it occurs sequentially through a narrow gate.