The Origin of Planetary Oxygen

About 2.5 billion years ago, our planet had no oxygen, and lifeforms were primitive. Then, oxygen levels suddenly spiked, the entire landscape of the planet changed, and we were on our way to complex life. Now, at last, we know why. A team led by Gustavo Caetano-Anollés of the University of Illinois have found the culprit behind the annihilation of the anaerobic organisms and the rise of oxygen-loving life. The answer: it is found in protein folds.

Folds are simply particular regions of a protein that serve specific functions. While the amino acids that make up these folds often mutate and transform, the folds themselves are extremely stable, retaining the same basic function for possibly billions of years. That makes protein folds one of our best shots at reconstructing the very earliest prehistory of the primordial Earth.

According to the timeline, protein folds existed 2.9 billion years ago that handled the synthesis of pyridoxal. This is simply an active form of vitamin B₆, which helps the smooth function of a range of protein enzymes in our bodies. Manganese catalase, an oxygen-producing enzyme, also appeared around 2.9 billion years ago. With these structures on board, cyanobacteria would have begun producing lots of oxygen.

-----

Kyung Mo Kim, Tao Qin, Ying-Ying Jiang, Ling-Ling Chen, Min Xiong, Derek Caetano-Anollés, Hong-Yu Zhang, Gustavo Caetano-Anollés. (2012). Protein Domain Structure Uncovers the Origin of Aerobic Metabolism and the Rise of Planetary Oxygen. Structure. Jan 11 Vol. 20 (1): 67-76. DOI: 10.1016/j.str.2011.11.003