Yo Protein, where you from again?
When you think of Protein, what comes to mind? Sculpted muscles? In school we may have learnt that it’s the building block of life, the sculptor of muscle, the master conductor of an array of cellular processes. But have you ever wondered “Where does protein really come from?”. Origin stories can often make for not only a fascinating story but a chance to learn something new about the protagonist. It’s a chance to gain a deeper level of understanding and appreciation - isn’t that what love is all about?
Spoiler alert: although we often associate protein with meat and muscle-bound bodybuilders putting in the reps at the beach, the answer lies buried deep in Earth’s history, long before Humans showed up to join the protein party with their protein bars and shakes.
13.8 billion year old soup
Billions of years ago, Earth's atmosphere crackled with energy, sparking a primordial soup of simple molecules. Among these were the building blocks of life: amino acids, the raw ingredients for proteins. However, these amino acids remained scattered and unconnected, like unbaked flour and sugar.
Then all of a sudden, Ribo Nucleic Acids (RNA), complex molecules with a knack for self-replication, emerged. Acting like primitive chefs, RNA molecules began to string amino acids together in specific sequences, forming short chain amino acids called peptides.
These RNA chefs showed promise because they could fold peptides into simple shapes, hinting at the potential for more complex structures.
Volcanic lightning and harsh UV radiation continued to bombard early Earth. In this harsh environment, only the most stable and functional peptides survived. These "super peptides" folded into intricate three-dimensional shapes, becoming the first true proteins.
Nitrogen - The missing ingredient
Now imagine this primordial soup is now teeming with potential. Simple molecules swirl about, waiting to be assembled into something grand. These are the amino acids, the building blocks of protein. Yet, a crucial ingredient remains locked away, out of reach: Nitrogen.
Most of Earth's nitrogen resided in the unreactive gas form (N2) in the atmosphere, unusable for building proteins. It was like having a pantry full of flour and sugar, but no yeast to make bread. If only we could sequester it from the air somehow. That would be an absolute game-changer because without Nitrogen, there would be no Life as we know it - every amino acid has an amino group (NH2) attached to the central carbon atom - more on this later. The absence of Nitrogen would leave a vacant spot that can’t be readily filled by other elements. As a result the entire process of protein synthesis would be disrupted. Say goodbye to basic cellular functions from building structures to carrying out enzymatic reactions. With protein synthesis grinding to a halt, life as we know it would simply not be possible. Even some of the simplest organisms rely on protein to function.
If people knew how important this was, they would be building shrines and paying homage to Usable Nitrogen in the form of NH2 on the regular. Anyways back to the story, at this point we know we need NH2 but who is metaphorically going to bring this to the table?
Enter the microscopic Nitrogen-Fixing Protein Gods!
Billions of years ago, the stage was set for a revolution. Bacteria, microscopic marvels with diverse talents, emerged as the unlikely heroes of this story. Among them were the nitrogen-fixing bacteria, possessing a remarkable enzyme complex called Nitrogenase.
One example of a bacteria blessed with this ability is Nostoc (pictured above), the most common genus of cyanobacteria that is found in both aquatic and terrestrial environments. It can provide its lucky host plant with Nitrogen through specialised nitrogen-fixing cells called heterocysts.
This bacteria’s enzyme can break the strong bonds of N2 and convert it into a usable form, like ammonia (NH3). With this "fixed" nitrogen, plants could grow more efficiently and abundantly resulting in a larger overall biomass of plants.
The Plant Kingdom: The Protein manufacturing plant (Geddit, geddit?)
With nitrogen fixation, plants, the green alchemists of Earth, could finally unleash their protein-synthesising potential. They utilised the fixed nitrogen provided by the bacteria to create a dazzling array of proteins. Amino acids, previously scattered and unconnected, were now readily available building blocks.
Plants obtain these amino acids through photosynthesis, using light energy from the sun to convert carbon dioxide and water into glucose. This glucose is then used to create the building blocks for amino acids which are then used to assemble complex proteins, all of which serve different roles.
Structural proteins, like the steel beams of a building, provided strength and support to cells. Transport proteins shuttled essential molecules across membranes, ensuring the proper functioning of the cellular machinery and so on.
It is interesting to consider that much like a solar panel, a living, growing plant is responsible for the process of converting the sun’s energy into both carbohydrates (energy) and protein stored in its biomass whilst storing both Carbon and Nitrogen sequestered from the atmosphere. The greater the biomass of the aggregate Plant Kingdom, the more carbohydrates and protein there are available to feed (directly or indirectly) the entirety of the Animal Kingdom.
Plants provide all 9 of the essential amino acids needed:
Phenylalanine
Leucine
Valine
Tryptophan
Threonine
Methionine
Lysine
Isoleucine
Histidine
In the diagram below, you can see the amino groups (H2N) attached to the central carbon atom where N stands for Nitrogen.
Herbivorous animals, lacking the ability to fix their own nitrogen, became reliant on consuming plants to obtain these essential protein building blocks.
With these building blocks, Prehistoric herbivores grew very large indeed and like plants, they became massive stores of energy as well as protein. However, unlike plants they could walk and do the things animals do, like poo and pee A LOT - this is part of the Nitrogen Cycle but we won't get into all that in this blog post. Understandably these ancient animals didn’t want to join the protein party and not bring anything to the table so they leveraged their own god-given gift - their bodies were able to synthesise non-essential amino acids. Non-essential amino acids are amino acids that your body can produce itself, even if you don’t get them from your diet.
With the following non-essential amino acids added, our list of nine has now swelled to a nice round number of twenty! 10. Alanine
11. Asparagine
12. Aspartic Acid
13. Glutamic Acid 14. Arginine 15. Cysteine 16. Glutamine 17. Tyrosine 18. Glycine 19. Proline 20. Serine
Naturally these proteins can’t be synthesised out of thin air. Many non-essential amino acids require essential amino acids as a raw material. For example the body can produce Tyrosine, a non-essential amino acid from the essential amino acid Phenylalanine through the enzyme phenylalanine hydroxylase and Cysteine can be derived from the essential amino acid Methionine.
To summarise, the Plant Kingdom manufactures the raw material amino acids. The Animal Kingdom uses that raw material to make some other amino acids. Caveat alert!! Although we understand that oversimplification comes at the cost of accuracy, what is simple and easy to understand (and 100% accurate) is that all those amino acid groups (that contains Nitrogen) came from plants and ALL amino acids essential or not have at least one of them.
From the intricate silk spun by a spider to the powerful muscles that propel a cheetah, life as we know it became possible thanks to the only true manufacture of protein that is the Plant Kingdom fueled of course by the nitrogen-fixing bacteria.
One of the consequences of oversimplification is that it may lead you to believe that sure, Plants manufacture the essential amino acids but only Animals can synthesise the non-essential amino acids but it may come as a surprise that infact all plants can manufacture all 20 amino acids - both the essential and non-essential amino acids! This is in contrast to Animals, who can only synthesise a subset of those amino acids.
"All plants can manufacture all 20 amino acids - both the essential and non-essential amino acids!"
The journey is the reward
If you’ve made it this far through protein’s journey through time, I hope that your perspective has changed a little because I know mine sure did. Before embarking on my own journey of discovery, I thought the protein building blocks of life came from meat (or protein powder, bars & shakes) and I’m sure this is still pretty much the understanding of the public at large today. This is why scenes like the one pictured below are commonplace.
“Choose your protein” the sign says at your typical salad bar. From the chickpea to the diced chicken to the selection of greens, they’re all made of the same amino acids. Of course the chicken has protein but where did that bird get its protein from? That question was one that is not often asked and understood. By now we know that those amino groups with Nitrogen or source protein can only be produced by the Plant Kingdom and Nitrogen-fixing bacteria partnership. Ironically the only true manufacture of source protein is under threat from deforestation to produce Animal Protein.
"Ironically the only true manufacture of source protein is under threat from deforestation to produce Animal Protein."
Livestock farming is an immensely inefficient method of producing protein and countering this is at the centre of Plantee's mission. Humanity has mostly chosen to do as little of the protein synthesis as possible. If LEGO was the analogue for protein, we don't want to build the lego, we want it ready-made when we unbox it - like wheres the fun and purpose in that? Not only is readymade LEGO what we want, but it forms our definition of what LEGO is.
We are all interconnected
The story of protein is a testament to the interconnectedness of life on Earth. Plants, with the help of bacteria, manufacture the proteins that all living beings rely on. We are all, in a sense, walking protein tapestries woven from the threads of this ancient partnership. We share the same set of 20 amino acids with every animal that has walked the earth since the beginning of time.
The future of all life however hangs in the balance and is again interconnected with the story of protein and our understanding of it. Not only does Humanity’s protein choice have a profound impact on Climate Change but it also deprives wildlife of their protein supply and homes.
The next time we have the luxury of choosing our protein, it might pay dividends to all current and future life to remember the origin story of protein. We are all interconnected. Choose source protein, choose life.