HOUSTON, Sept. 25 (UPI) -- The stable properties of proteins in whale blood, which allow them to dive deep into the ocean and remain active while holding their breath for up to two hours, may prove to help researchers develop synthetic blood that could be used in transfusions for trauma patients.
Myglobin holds oxygen in muscle cells for them to use. Marine mammals have ultra-stable myoglobin that can hold oxygen longer, and their bodies produce significantly more of it in order to hold more oxygen in reserve.
"Whales and other deep-diving marine mammals can pack 10 to 20 times more myoglobin into their cells than humans can, and that allows them to 'download' oxygen directly into their skeletal muscles and stay active even when they are holding their breath," said John Olson, a biochemist at Rice University, in a press release. "Our results confirm that protein stability is the key."
The globin family of proteins is shaped around a pocket, where heme is stored. The heme pocket opens and closes, trapping and releasing oxygen. Researchers developed a method to test myoglobin expression outside living cells, which allowed them to find the amount of myoglobin expressed was dependent on the ability of the protein to retain its shape before binding to heme.
The researchers focused on apomyoglobin, a heme-free form of myoglobin, which in marine mammals is 60 times more stable than in humans. While the overall shapes of the forms of globin are similar, the researchers found differences in their amino acid sequences allow the heme-free version to retain its shape much longer.
Researchers compared myoglobin from humans, pigs, goosebeak whales, gray seals, sperm whales, dwarf sperm whales and three mutant forms constructed in previous work by one of the researchers on the team. They found the stability of apoproteins was tied to expression levels of myoglobin -- especially those with lower heme affinity.
"This work is very important for our projects on synthetic blood substitutes and determining the toxicity of acellular hemoglobin," he said. "Premila [Samuel, another researcher in the study] has laid the groundwork for high-throughput screening of large libraries of hemoglobin variants without the need for purifying milligram quantities of pure protein. This method is a big step forward in our efforts to identify more stable recombinant hemoglobins."
The study is published in the Journal of Biological Chemistry.
