The origin of ion-pumping proteins could explain how life began in, and escaped from, undersea thermal vents.
Rocks, water and hot alkaline fluid rich in hydrogen gas spewing out of deep-sea vents: this recipe for life has been championed for years by a small group of scientists. Now two of them have fleshed out the detail on how the first cells might have evolved in these vents, and escaped their deep sea lair. Nick Lane at University College London and Bill Martin at the University of Düsseldorf in Germany think the answer to how life emerged lies in the origin of cellular ion pumps, proteins that regulate the flow of ions across the cell's membrane, the barrier that separates it from the outside world.
In all cells today, an enzyme called ATP synthase uses the energy from the flow of ions across membranes to produce the universal energy-storage molecule ATP. This essential process depends in turn on ion-pumping proteins that generate these gradients. But this creates a chicken-and-egg problem: cells store energy by means of proteins that make ion gradients, but it takes energy to make the proteins in the first place. Lane and Martin argue that hydrogen-saturated alkaline water meeting acidic oceanic water at underwater vents would produce a natural proton gradient across thin mineral 'walls' in rocks that are rich in catalytic iron–sulphur minerals. This set-up could create the right conditions for converting carbon dioxide and hydrogen into organic carbon-containing molecules, which can then react with each other to form the building blocks of life such as nucleotides and amino acids.
The rocks of deep-sea thermal vents contain labyrinths of these tiny thin-walled pores, which could have acted as 'proto-cells', both producing a proton gradient and concentrating the simple organic molecules formed, thus enabling them eventually to generate complex proteins and the nucleic acid RNA. These proto-cells were the first life-forms, claim Lane and Martin.