DNA may provide the core instructions for making life, but it’s the proteins it codes for that actually gets on and does the work – a recipe book can’t bake a cake after all. As a result of billions of years of evolution, the animal kingdom today contains some beautiful, useful and frankly phenomenal proteins.
Here are ten such proteins, in no particular order. Click any image to be taken to the source.
10 – Crotoxin
When they feel threatened or go in for the kill, venomous snakes spit out a cocktail of hundreds of different enzymes and other proteins. For the South American rattlesnake (Crotalus durissus terrificus) the main weapon of choice is crotoxin, which works in many harmful ways but is best known as a paralysing neurotoxin.
Crotoxin is made up of two protein subunits called CB and CA, which can be thought of as a deadly missile and its add-on homing device respectively. CB on its own is powerful but not very specific in where it hits. The true potency is unleashed only when CB combines with CA, chaperoning it to the places where it’ll have the stronger effect.
Perhaps unexpectedly, crotoxin and other snake venom components may soon because vital components of cancer treatment!
9 – Thermogenin
When we get a bit chilly, it often helps to run around as a way of warming up. This is because exercise creates an energy demand which is met by the mitochondria – the engines of every cell. Like any engine, mitochondria are not 100% efficient and some heat will be produced as a byproduct. Small mammals coming out of hibernation and human babies are not able to get up and frolic about easily, but they have another trick courtesy of a protein called thermogenin or UCP1.
This protein works in the mitochondria of specialised fat cells by kicking the engine out of gear while simultaneously revving it furiously. The result is a lot of excess heat produced without any extra activity or even the conscious thought required to put on a jumper.
8 – GFP
GFP stands for Green Fluorescent Protein and is special for both its visual impressiveness and its usefulness to science. It’s naturally found in a jellyfish species where its only “job” is to absorb blue and UV light and emit an eerie green colour in return.
This might not sound desperately useful but since the protein was first extracted in the 1960s and then mutated slightly to make it brighter and more stable, it’s been a favourite among cell biologists all over the world. This is because they can connect GFP up to any other protein of interest, creating a green fusion protein. They can then track the green colour around the cell and learn more about what their protein is doing and why – helpful in everything from cancer research to reproductive studies. GFP has even been used to create a genetically modified kitty. This cat is perfectly healthy, but has a distinct glow-in-the-dark green tinge when placed in UV light.
7 – Antifreeze proteins
Life as a fish in a cold climate is tough, and the biggest threat is ice forming from within – bursting cells open and causing general devastation. Yet life is nothing if not adaptive – even in the coldest waters of the Arctic and Antarctic you’ll find fish swimming around, unarguably not frozen! This is because the tissues of fish like the winter flounder are packed with antifreeze proteins (AFPs). These proteins do the same job as the stuff we put in our car engines but much more efficiently. AFPs actually bind to microscopic ice crystals as they form and prevent them growing any bigger, allowing the flounder to carry on with his fishy business without ending up in the freezer section.
6 – Silk proteins
Silk isn’t seen so much in these days of cotton/polyester mixes but clothing made from silkworm spit has been the height of fashion and a show of wealth for thousands of years. Silkworms are not actually worms, but the caterpillar of the moth Bombyx mori. When the caterpillar is ready for metamorphosis, it’ll start spinning a single thread of protein fibre around itself which can be up to a mile long but thin enough to be barely visible. It does this for its own protection during this vulnerable stage but humans had other ideas in mind…
If you boil the cocoon in water for a few minutes, it kills the insect and makes it quite easy to extract the thin, long and strong thread. According to Chinese legend, silk was first discovered around 2700 BCE by Chinese empress Lei-tzu when a cocoon fell into her cup of tea!
5 – Whale myoglobin
Sperm whales are champion endurance divers and can make one large gulp of air last up to 90 minutes. Before it goes under, the whale spends a few minutes at the surface taking in as much oxygen as possible. The oxygen is delivered to muscle tissues where it quickly binds to a protein called myoglobin. Towards the end of the dive when the blood oxygen has been all but lost, myoglobin acts like an emergency ration pack for muscle cells, keeping them going until the whale resurfaces. Humans do have myoglobin but in such a relatively pitiful amount that even five minutes is impressive!
The muscles of whales are so packed full of deep red myoglobin that the meat actually looks black. At these concentrations, proteins generally clump together in unhealthy aggregates but it was recently discovered that myoglobin of marine mammals is strongly charged so the proteins actually repel each other to avoid sticking together.
4 – PfEMP-1
This one isn’t actually from an animal but from the single-celled parasite responsible for malaria and therefore half a million deaths every year – Plasmodium falciparum.
Part of the parasite’s life cycle involves hijacking and wreaking havoc on our red blood cells (RBC) in which they multiply. Our immune system has ways of detecting infected cells and raising a targeted antibody army destroy them to contain the parasite, but Plasmodium has a proteinaceous Ace up its proverbial sleeve.
It forces the RBC to display a protein called PfEMP-1 on its surface which makes it stick to the blood vessel wall where it’s less likely to be detected. Even if the infected cell is found, it takes a few days for the immune system to raise up enough destructive antibodies. In that time, the exact version of PfEMP-1 expressed on the RBC (there are about 60 options) will shift just enough to avoid detection. The immune system will have to start over again while the parasite keeps on multiplying.
3 – Vitellogenin
Honeybees are in trouble all over the world, and there’s way more at stake than the loss of (a) yet another creature from this planet, and (b) delicious honey. It’s estimated that $15 billion worth of crops each year only make it onto our plates because of the work of bees but the 30% annual loss being reported is unsustainable.
Pesticides and parasites are bearing the brunt of the blame but we don’t really know what’s going wrong. However an interesting protein called vitellogenin may help us understand. “The more vitellogenin in bees, the longer they live… it also supports the immune function and is an antioxidant that promotes stress resistance”, explains Dr Havukainen from the Norwegian University of Life Sciences.
Knowing more about this protein which seems so intrinsically linked with the health of bees could help bring colony numbers back up. After all, a wise man once said: “Knowing is half the battle!”.
2 – GP-9
Would you rather be ruled over by a single queen, or many? For the fire ant species Solenopsis invicta, the answer is decided by just one protein called GP-9. This is a protein found on ants’ antennae, and normally allows worker ants to detect and viciously attack any intruding queens other than the One True Queen to which they are all related.
So far, so straightforward, but sometimes an ant colony will arise with a mutated version of this protein which provides an interesting and unexpected effect. The ability of the worker ants to detect foreign queens seems to be impaired, so they are able to safely enter the colony and start laying their own eggs… but only if they have the same mutation as the workers. “Normal” queens are still spotted and killed, but multi-queened colonies which have only the mutated protein in common end up living harmoniously together.
1 – BMP-4
Apart from the frankly horrific appendage of the male duck and a few others, most birds lack penises. Instead they have a general-purpose opening called a cloaca from which all bodily fluids exit. Surprisingly bird embryos begin to develop phalluses but development is halted and reversed before hatching. The protein responsible for the doomed bird penis is called BMP-4. It’s expressed throughout the chicken penis much more than for ducks and causes programmed cell death.
Why did this unexpected trait evolve, given certain obvious merits of penises compared to awkward “cloacal kisses”? We know BMP-4 has many other functions in creating a healthy bird, so this could simply be an evolutionary side-effect. Alternatively, given how vicious ducks are with their large penises, perhaps female birds only allowed mates with small penises to mate, to the point where it actually disappeared completely!