A proton pump is an integral membrane protein that transfers protons through the membrane of cells, mitochondria, or another intracellular compartment. Proton pumps catalyze the following reaction:
H+[on one side of a biological membrane] + energy ⇌ H+[on the other side of the membrane]
Mechanisms are based on energy-induced conformational changes of the protein structure or on the Q cycle.
In bacteria producing ATP, the energy used to transfer protons is produced in the electron transport chain or by photosynthesis.
Bacteriorhodopsins are a family of archaeotic membrane photosensitive proteins (e.g. halobacteria). Bacteriorhodopsins carry out proton transfer through the plasma membrane, similar in structure to mammalian rhodopsins.
This protein performs the same function as chlorophyll in other organisms - it converts the energy of sunlight into the energy of chemical bonds. It acts as a light-dependent proton pump. The absorption of a quantum of light leads to rapid structural changes in the molecule, due to which the transfer of the hydrogen cation from the cytoplasm to the outside of the cell membrane occurs.