The first breath: oxygen becomes a friend

Scientists have pointed to a living organism that has learned to ...
Perhaps the most important change that has gone through life on earth in its history, occurred 2.3 billion years ago, when the bacteria - then the only inhabitants of the planet - have learned to use oxygen more accumulated in the environment and representing a growing threat. It was then that began to appear the first aerobic organisms, which, as we are, just in need of free oxygen for their energy systems.

And recently, scientists from the team of Professor Gustavo Caetano - Anollya (Gustavo Caetano-Anollés) was something quite astonishing: to find, perhaps, the first representative of our aerobic world. For this, they did not carry out any excavations and fossils studied. Together with colleagues from China and South Korea, scientists have identified a large-scale comparison of protein domains is quite old and have tried to trace their historical destiny.

The spatial domain shape - large ... Therefore, the form domain is usually exposed to volatility in the course of evolution is much weaker than the primary amino acid sequence of the protein chain. Verified on a set of characteristics, scientists classify the shape of domains and divide them into many groups.

At the same proteins may include one or more identical or different domains, and sometimes acquire new or lose unnecessary, even share. These processes, according to the authors, make it difficult to ... Therefore, they examined only the whites, first, related to the aerobic (... In consideration of the data were collected by representatives of all known groups of living organisms, except viruses.

As a result, scientists have built a historical sequence of appearance and evolution of the domain associated with aerobic metabolism, and then compared it with the scale of the major events in the development of life on Earth - such as the emergence of aerobic organisms, or eukaryotes. Both sequences perfectly coordinated with each other.

The authors found that the most ancient biological aerobic process was the synthesis of pyridoxal, one of the active form of vitamin B6. This reaction is the living organisms have started already about 2.9 billion years ago, catalyzing it with the manganese enzyme catalase, which is more known for being extremely active molecule decomposes hydrogen peroxide to protect cells from its harmful oxidizing effects.

According to scientists, these ancient organisms get oxygen to produce pyridoxal was the reaction in which hydrogen peroxide decomposes into water and free oxygen. And with an excess of hydrogen peroxide, they met, possibly as a result of the bombing of a powerful ice water with ultraviolet rays of the sun: even without the oxygen of the atmosphere and its ozone layer, the Earth has been protected from their influence is much weaker than it is today.