The quest to concoct a working blood substitute could get a boost from superpowered proteins derived from whale blood.
Although we’ve made great strides in increasing the supply of blood donations, we’re still very far from giving timely access to every patient in need of a transfusion. Blood donations also carry the risk of transmitting infections, and even a simple labeling mistake can result in catastrophe if a patient accidentally receives the wrong blood type.
For decades, scientists have been working to create a synthetic blood substitute that can safely meet the great demand for transfusions. Unfortunately, blood is a tricky solution to replicate because it’s full of a huge variety of cells and protein types unique to each person. Its most important function is fulfilled by the protein hemoglobin, which stores oxygen and carries it throughout the body. So far, scientists have been unable to manufacture a version of hemoglobin that survives and functions outside of red blood cells.
Since hemoglobin was proving so difficult to work with, John Olson’s team at Rice University turned to other oxygen-carrying proteins in other animals. In doing so, they may have discovered the key to synthetic blood flowing through the arteries and veins of whales.
Whales are masters at strategically storing and using oxygen, thanks to a protein called myoglobin. Like hemoglobin, myoglobin binds oxygen, but only inside muscle cells. Although humans and other mammals also express myoglobin, it works much more efficiently in whales. With every dive, they can pack 10-20 times more myoglobin into their muscle cells, allowing them to hold their breath for up to two hours even while actively using their muscles.
Myoglobin can only bind oxygen after first binding a chemical structure called a heme group. The heme-free version of myoglobin, called apomyoglobin, stays intact even outside of living cells. The scientists tested the stability of apomyoglobins from different organisms by applying measured amounts of chemicals that induce the protein to unfold from their 3D configuration. The whale proteins needed 60 times more chemicals to unfold, which implied greater stability than apomyoglobin from humans. This comes from very slight differences in the sequence of amino acids which make up each protein. Different types of amino acids can bind each other at various strengths, which changes the final 3D structure and stability of the protein.
The researchers hypothesize that these slight amino acid differences are also the reason why whales can fit so much more myoglobin in their muscles. But most importantly, the stability of the apoprotein seems to correlate with how much protein can be produced. That’s what piqued the interest of Olson’s researchers, because their attempts at driving E. coli to synthesize hemoglobin had stalled before production reached a high enough yield for a working blood substitute.
By incorporating characteristics of whale myoglobin into a new version of hemoglobin, Olson hopes to finally develop a product that can efficiently deliver blood, persist outside of living red blood cells, and be easily produced on a mass scale. This discovery has laid the most comprehensive groundwork yet for a synthetic blood substitute, and could revolutionize the treatment of trauma patients.