Origin of photosynthetic water oxidation at the dawn of life

摘要: Oxygenic photosynthesis starts with the oxidation of water to O2. Cyanobacteria are only known prokaryotes capable oxygenic and therefore, it is assumed that a late innovation relative origin life. However, when exactly originated remains lively debated. Here we show photosystem II, water-splitting enzyme, occurred at an early stage during evolution life long before Cyanobacteria. We use relaxed molecular clocks, ancestral sequence reconstruction, comparative structural biology demonstrate II exhibits patterns through geological time indistinguishable from those ATP synthase, RNA polymerase, or ribosome, some oldest enzymes. Our work suggests establishment bioenergetics reaching farther into past than can be documented based on species trees alone.