Biological complexity: utilizing highly toxic selenium (Introduction)

by David Turell , Friday, June 17, 2022, 19:03 (680 days ago) @ David Turell

The very reactive antioxident is part of an essential amino acid and invovled in many biochemical processes:

https://phys.org/news/2022-06-vital-cellular-machinery-body-incorporation.html

"A Rutgers scientist is part of an international team that has determined the process for incorporating selenium—an essential trace mineral found in soil, water and some foods that increases antioxidant effects in the body—includes 25 specialized proteins, a discovery that could help develop new therapies to treat a multitude of diseases from cancer to diabetes.

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"First, selenium is encapsulated within selenocysteine (Sec), an essential amino acid. Then, Sec is incorporated into 25 so-called selenoproteins, all of them key to a host of cellular and metabolic processes.

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"The incorporation of selenium takes place deep within an individual cell's intricate machinery. Scientists already knew which proteins and molecules of RNA—a nucleic acid present in all cells involved in the production of proteins—enabled the process. However, they were not able to discern the critical step of how these factors worked in tandem to complete the cycle, dictating the function of the cell's ribosome—a large macromolecular machine that binds RNA to make more proteins. What they found was that the processes that occur are not like any understood to take place anywhere else in the human body.

"'This amino acid gets attached to a unique RNA molecule and that has to be carried to the ribosome via a unique protein factor," said Copeland, whose lab has spent the past 20 years working to understand how these biomolecules function on a biochemical level. "And all of this evolved in humans specifically to allow selenium to be incorporated into this handful of proteins."

"Once Sec is ensconced in the selenoproteins, the proteins perform a wide range of vital functions necessary for growth and development. They produce nucleotides, the building blocks of DNA. They break down or store fat for energy. They create cell membranes. They produce the thyroid hormone, which controls the human body's metabolism. And they respond to what is known as oxidative stress by detoxifying chemically reactive byproducts in cells.

"Diseases and disorders such as cancer, heart disease, male infertility, diabetes and hypothyroidism can arise when the production of selenoproteins is disrupted."

Comment: selenium, a trace element vital to life, is found in volcanic soils. Large amounts are highly toxic, so we humans must take in only one two micrograms a day. But high in the Andes llamas have adapted to the selenium abundance in those soils and injest at least two milligrams a day. If selenium is so hard to handle and kills, why did it appear in life? A designer can do this, but chance development is not reasonable.