You’ve undoubtedly heard of protein, and you probably know it’s important for your health. But what is it?
In brief, proteins are chains of amino acids. Although your body uses just 20 or so amino acid building blocks, proteins come in near-infinite forms.
Using different combinations of amino acids in varying orders changes how these acids behave. And by folding these long chains into complex 3D structures, you get even more variety.
Every cell in your body contains protein. It’s vital for your metabolism, and it forms structures like skin, hair, and bones.
Protein also makes your muscles work, and it carries oxygen around your body. The list goes on and on.
Without protein, you wouldn’t exist. And neither would any life on Earth.
In this feature, we’ll look at some of the most fascinating proteins that are busy working in your body as you scroll through this article.
Let’s start with the largest protein, shall we?
The Titan protein
Titin — short for “Titan protein” — is the biggest known protein in humans. It’s built from around 27,000 amino acids.
For a little perspective, insulin, which is an incredibly useful protein, is just 51 amino acids long.
Titin accounts for an impressive 0.5 kilograms (1 pound) of your total body weight.
It forms part of the sarcomere, the basic unit of muscles. Sarcomeres are responsible for making your muscles contract.
As you might imagine, such a giant protein has a number of jobs.
For instance, it has an anchoring role: It ensures that other muscle proteins stay in the right place as your muscles contract.
Titin also acts like a "molecular spring", allowing your muscles to stretch. So, it helps provide structure while also keeping your muscles flexible.
Problems with titin are linked to a range of muscle conditions, including some that affect the muscle tissue of the heart.
Titin comes in different forms, some of which are “stiffer” than others. And some scientists think that the ratio of these forms in cardiac muscle might play a part in heart disease.
So, researchers are investigating whether targeting titin might one day help treat some heart problems, such as heart failure.
Topoisomerases: The great untanglers
DNA forms a double helix. In other words, it’s two long chains twisted together. And for DNA to replicate, it needs to unwind these strands.
As this happens, there’s a good chance that the strands will get tangled up. Anyone who’s ever tried to pull a cable out of a drawer full of cables will understand.
The strands can get too coiled, which scientists call "supercoiling." And sometimes, they even tie themselves in knots.
This is bad news because once the strands are tangled, the DNA can’t replicate, and the cell may die.
Even as scientists were first figuring out the structure of DNA, they realized this could be a problem.
Some wrote: “Since the two chains in our model are intertwined, it is essential for them to untwist if they are to separate. [...] Although it is difficult at the moment to see how these processes occur without everything getting tangled.”
But don’t worry, topoisomerases are here to save the day. They’re professional DNA untanglers. They make sure DNA is coiled just the right amount, and they undo any knots that form.
In fact, topoisomerases are so important that all of your cells contain them.
And because they’re vital for cell survival, scientists are testing whether interfering with topoisomerases in cancer cells might be a good way to fight the disease.
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Sonic hedgehog protein
We could have included this protein based on its name alone. But it’s also an incredible enzyme, so it’s earned its place on this list twice.
Beyond its etymological wonder, Sonic hedgehog protein (SHH) is almost impossibly important.
It provides a chemical signal that plays a pivotal role as an embryo grows.
The protein and its signaling pathway help the embryo develop correctly, which includes making sure that limbs and organs are in the right shape and place.
Its signal is also vital for the developing brain. For example, it makes sure that your brain's left and right hemispheres are split in the right place.
SHH and its pathway also ensure that you have two eyes, rather than just one in the middle, and that your face develops in other ways.
Scientists know less about what SHH does during adulthood, but there’s some evidence that it might be involved in growing new neurons and protecting against inflammation in your brain.
Plus, SHH may play roles in lung and metabolic health.
Why the name? There are actually a number of hedgehog proteins, including Indian hedgehog and desert hedgehog. The names came about during early research in fruit flies.
Scientists found that when a fly’s hedgehog genes don’t work, its larvae develop spike-like protrusions called denticles all over their bodies. So, they kind of look like hedgehogs.
Finally, we should mention that SHH is blocked by a compound called Robotnikinin, named after Sonic’s nemesis, Robotnik, so that’s nice.
The NOX family
Many of you will be familiar with the term “antioxidants.” These compounds protect your health by mopping up highly reactive, unstable chemicals called reactive oxygen species (ROS).
If ROS are left hanging around where they’re not supposed to be, they can destroy your cells.
Because of this, ROS are implicated in various health conditions, including cancer.
Understandably, ROS are considered the bad guys — they can kill cells, after all — but that’s not the whole story.
They also play essential roles in cell signaling, cell growth, and your immune system, and that’s where the NOX family comes in.
NADPH oxidases, which are part of the NOX family, are basically the opposite of antioxidants — they help produce ROS.
But, as part of an immune response, they use their ROS firepower for good rather than evil. NADPH oxidases trigger “oxidative bursts” of ROS that kill invading microbes.
Scientists worked out how important these proteins were by studying people with a condition called chronic granulomatous disease.
This condition is caused by a defect in a NOX family enzyme. Without the enzyme’s oxidative bursts, a person becomes more susceptible to bacterial and fungal infections.
They also experience other health problems, including severe inflammation, which some experts call hyperinflammation.
Beyond the immune system, these proteins also help maintain a healthy cardiovascular system, regulate kidney function, and do other important jobs.
What’s also cool is that NOX-like proteins seem to have first evolved more than 3.5 billion years ago.
In other words, organisms have probably been fighting off other organisms using dangerous, unstable chemicals almost since life began.
We started this article with a giant protein, so we’ll end with a really tiny one: glutathione. It’s just three amino acids long.
Technically, because of its length, it’s a peptide rather than a protein, but we hope you’ll forgive us.
And don’t let its diminutive size fool you — glutathione is a big player in your insides.
Your cells have high concentrations of this peptide. In fact, your levels of glutathione are similar to those of more famous molecules like glucose and cholesterol. That’s a sign that it might be up to something important.
One of glutathione’s main jobs is protecting against ROS — those dangerous, cell-killing chemicals we met earlier.
Aside from protecting against free radicals, it also helps cells eliminate toxic chemicals like mercury and organic pollutants. And it’s vital for the smooth running of your mitochondria — the fabled powerhouses of the cell.
And if that’s not enough, glutathione is also important for cell growth and division.
Meanwhile, scientists have linked lower glutathione levels to cognitive decline and Alzheimer’s disease. And problems with this peptide might play a part in Parkinson’s disease, some lung conditions, and other health issues.
In other words, glutathione is the very definition of small but mighty.
The last word
If nothing else, we hope this journey has given you a deeper appreciation of the variety of proteins in your body. All of them work tirelessly to keep you ticking over.
The fact that, say, 20-something amino acids can be combined to provide such a range of functions is nothing short of magical.
So, next time you eat something containing a lot of protein — like a peanut — feel free to daydream about where those amino acids will end up once your digestive system has broken the protein down.
Maybe they’ll help your muscles contract, get busy untangling your DNA, or clear up dangerous compounds. Or prehaps they’re destined to use powerful chemicals to destroy invading microbes.
Proteins are wonderful. And we still have much to learn about them.
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