Evolution and humans: our protein production (Evolution)

by David Turell @, Monday, October 22, 2018, 15:01 (52 days ago) @ David Turell

We don't make as many basic proteins as some animals, but with modifications to the molecules we create a massive number of special ones:

https://cosmosmagazine.com/biology/proteins-wear-clothes-and-understanding-their-fashio...

"Humans produce 20,418 proteins, and convert them into one million variations. It's important to understand why, say Pedro Beltran-Alvarez and John Greenman, from the UK's University of Hull.

"We humans are top of the evolutionary tree, the most complex organisms that have ever lived on Earth in five billion years. Right? One way we might actually prove our biological complexity is to look at the number of different proteins that our bodies can produce for building all our different types of cells and the other things they need.

"This number is approximately 20,418 in humans. We are clearly more complex than chickens (18,346), flies (13,931) and bacteria, some of which can produce only a few hundred different proteins. But here is the humbling news: some crustaceans can make up to 30,000 proteins and a red cabbage has nearly 60,000 different proteins.

"Scientists have managed to come up with an explanation for this apparent conundrum and save our dignity as a species. One of the features that make us more complex than a cabbage is what’s called post-translational modifications of proteins, the way proteins can change after they are copied from our DNA. If we take these into account, then the total number of different proteins in human cells is an estimated one million.

***

"Just like humans, the proteins in our bodies are born without any clothing. But before getting to work and socialising with other proteins, most of them undergo the equivalent of getting dressed. These items of protein clothing can change the “naked” protein’s structure, function and how it interacts with other proteins. So protein clothing contributes hugely to the complexity of our bodies.

"The analogy works in different ways. Just as there is only one place where you can (comfortably) wear a left-hand glove and your reading glasses will not work if you put them on your feet, proteins can only wear their modifications at specific sites on their structure for them to work.

"Protein modifications can also be reversed. Just as we can take off a jacket if we’re too hot, proteins can have some items of clothing, such as phosphate groups, removed in a fraction of a second. But other modifications are very stable. For example, if methyl or lipidic groups are added to proteins they are like “tattoos” that are very difficult to remove.

"Again like us, proteins can wear many different items of clothing at the same time. In some cases, these different modifications can interact with each other and also affect what other changes can be made to the protein."

Comment: the article goes on to explain how protein analysis and modification can help us fight cancer and diseases. I've presented it to make the point that our genome with 20,000+ genes has many complex tricks to make us so special and so different/distant from our primate relatives


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