Evolution: ribosomes flexible, ancient (Evolution)

by David Turell @, Saturday, November 17, 2018, 19:10 (221 days ago) @ David Turell

By cut and past this study altered ribosomes radically and they still worked with the conclusion they were very flexible at the start of life:


"This experiment had a good chance of crashing. Instead, it delivered whopping evidence to corroborate the earliest evolution of the translational system, the mechanisms which make life out of our genes. The study swapped out all its magnesium, tabula rasa, and showed that the system, centering on the ribosome, would have thrived basically as it is today 4 billion years ago at the earliest foundations of life on Earth.


"In the system inside cells that translates genetic code into life, he replaced about 1,000 essential linchpins with primitive substitutes to see if the translational system would survive and function. It seemed impossible, yet it worked swimmingly, and Bray had compelling evidence that the great builder of proteins was active in the harsh conditions in which it evolved 4 billion years ago.

"The experiment's success reaffirmed the translational system's place at the earliest foundations of life on Earth.

"Every living thing exists because the translational system receives messages from DNA delivered to it by RNA and translates the messages into proteins. The system centers on a cellular machine called the ribosome, which is made of multiple large molecules of RNA and protein and is ubiquitous in life as we know it.


"In today's ribosome, and in the whole translational system, they are magnesium ions, and Bray's experiment replaced them all with iron ions and manganese ions, which were overabundant on primordial Earth. Williams and Jennifer Glass, the principal investigators in the new study, also had their doubts this was doable.

"I thought, 'It's not going to work, but we might as well try the moonshot'," said Williams who has led similar work before but on simpler molecules. "The fact that swapping out all the magnesium in the translational system actually worked was mind-boggling."

"That's because in living systems today, magnesium helps shape ribosomes by holding them together. Magnesium is also needed for some 20 additional enzymes of the translational system. It's one reason why dietary magnesium (Mg) is so important.

"The number of different things magnesium does in the ribosome and in the translational system is just enormous," said Williams. "There are so many types of catalytic activities in translation, and magnesium is involved in almost all of them."


"Bray incubated ribosomes in the presence of magnesium, iron, or manganese inside a special chamber with an artificial atmosphere devoid of oxygen, like the Earth four billion years ago.

"He found that the magnesium replacement went far beyond atoms in the ribosome.
"Surrounding the ribosome is also a huge cloud of magnesium atoms. It's called an atmosphere, or shell, and engulfs it completely. I replaced everything, including that, and the whole system still worked."

"Eons down the road, the evolution of the translational system in the presence of magnesium may have given it an adaptive advantage. As oxygen levels on Earth rose, binding up free manganese and iron, and making them less available to biology, magnesium probably comfortably assumed the thousands of roles it occupies in the translational system today.

Comment: This theoretical conclusion from this study supports the concept of initial design which was flexible enough to use what metals were available at different points in the Earth's evolution

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