evolution: finding tiny proteins (Introduction)

by David Turell , Monday, October 21, 2019, 22:37 (1650 days ago) @ David Turell

The last entry discussed large complex protein molecules. This describes new;y discovered tiny proteins taht seem to have enormous influence on large protein functions:

https://www.sciencemag.org/news/2019/10/new-universe-miniproteins-upending-cell-biology...

"On a treadmill, the mice could scurry up a steep 10% grade for about 90 minutes before faltering, 31% longer than other rodents. Those iron mice differed from counterparts in just one small way—the researchers had genetically altered the animals to lack one muscle protein. That was enough to unleash superior muscle performance. "It's like you've taken the brakes off," Olson says.

"Just as startling was the nature of the crucial protein. Muscles house some gargantuan proteins. Dystrophin, a structural protein whose gene can carry mutations that cause muscular dystrophy, has more than 3600 amino acids. Titin, which acts like a spring to give muscles elasticity, is the biggest known protein, with more than 34,000 amino acids. The protein disabled in the mice has a paltry 46. Although researchers have probed how muscles work for more than 150 years, they had completely missed the huge impact this tiny protein, called myoregulin, has on muscle function.

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"Biologists are just beginning to delve into the functions of those molecules, called microproteins, micropeptides, or miniproteins. But their small size seems to allow them to jam the intricate workings of larger proteins, inhibiting some cellular processes while unleashing others. Early findings suggest microproteins bolster the immune system, control destruction of faulty RNA molecules, protect bacteria from heat and cold, dictate when plants flower, and provide the toxic punch for many types of venom. "There's probably going to be small [proteins] involved in all biological processes. We just haven't looked for them before," says biochemist Alan Saghatelian of the Salk Institute for Biological Studies in San Diego, California.

"Small proteins also promise to revise the current understanding of the genome. Many appear to be encoded in stretches of DNA—and RNA—that were not thought to help build proteins of any sort. Some researchers speculate that the short stretches of DNA could be newborn genes, on their way to evolving into larger genes that make full-size proteins. Thanks in part to small proteins, "We need to rethink what genes are," says microbiologist and molecular biologist Gisela Storz. (my bold)

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"Being small limits a protein's capabilities. Larger proteins fold into complex shapes suited for a particular function, such as catalyzing chemical reactions. Proteins smaller than about 50 to 60 amino acids probably don't fold, says chemist Julio Camarero of the University of Southern California in Los Angeles. So they probably aren't suited to be enzymes or structural proteins.

"However, their diminutive size also opens up opportunities. "They are tiny enough to fit into nooks and crannies of larger proteins that function as channels and receptors," Olson says. Small proteins often share short stretches of amino acids with their larger partners and can therefore bind to and alter the activity of those proteins. Bound microproteins can also shepherd bigger molecules to new locations—helping them slip into cell membranes, for instance."

Comment: short modifications of large proteins, by having the small proteins inserted into larger ones is a neatly designed way to alter function on the fly. Further note these are the result of DNA and RNA work considered to come from 'junk' DNA, again reducing the amount of so-called junk DNA. Discoveries like this are pointing to the necessary conclusion that it is all designed.