Woolly Mammoth Blood Breathes Again

Posted on September 22, 2011 by

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Woolly mammoth skull at the American Museum of Natural History

Researchers in the lab of Chieng-Ho, of Carnegie Mellon University, have published a detailed comparison between the hemoglobin of living elephants and extinct woolly mammoths.

Hemoglobin is the protein that makes the crime scenes in CSI red – at least, it would do if they used real blood and not just corn syrup. The job of real hemoglobin is to transport oxygen to where it is needed in your body. It can do this because it binds tightly to oxygen in the oxygen-rich blood of your lungs and doesn’t let go of it until it reaches the oxygen-poor blood in the other parts of your body.

That ‘letting go’ process is crucial, since the oxygen has to be released from hemoglobin to be used to produce energy. This process is even more efficient when you are exercising hard, because all the heat that builds up in those pumping muscles favors the deoxygenation of hemoglobin.

But of course, the reverse is also true. Cold temperatures make it much more difficult for hemoglobin to let go of oxygen. So how does hemoglobin function in animals that live in very cold environments like the arctic?

The best way to understand the tweaks that allow hemoglobin from cold-adapted species to function is to compare the hemoglobins of two closely-related species – one species from a warm environment and one species from a freezing environment. Like asian elephants and woolly mammoths, for example. The fact that mammoths have been extinct for thousands of years hasn’t stopped researchers from Carnegie Mellon from making just that comparison.

As part of an international collaboration, they have used the DNA sequences preserved in a 43,000 year old mammoth bone from Siberia to reconstruct woolly mammoth hemoglobin in modern-day bacteria. Last year, the group showed that there were only three significant DNA mutations that distinguished mammoth from elephant hemoglobin. When the hemoglobin genes were introduced into the bacterium Escerichia coli, it used the gene to make hemoglobin protein, which was then purified for further study. The three mutations that distinguished the two genes resulted in significant differences in the properties of the hemoglobin, including apparent differences in the effect of cold temperatures.

Last week, the group published more detailed studies of these lab-made hemoglobins, confirming that oxygen binding by mammoth hemoglobin is less sensitive to temperature changes, and laying the groundwork for understanding these differences at a molecular level. Their ultimate hope is that they can use their understanding of mammoth hemoglobin to help design synthetic blood products for use during surgical procedures that require hypothermic conditions.

But even beyond the importance of hemoglobin itself, these studies have pioneered an entirely new approach to studying the biology of extinct organisms. Think CSI: Pleistocene.

Reference:

A biochemical-biophysical study of hemoglobins from woolly mammoth, asian elephants, and humans.

Yue Yuan, Tong-Jian Shen, Priyamvada Gupta, Nancy T. Ho, Virgil Simplaceanu, Tsuey Chyi S. Tam, Michael Hofreiter, Alan Cooper, Kevin L. Campbell, and Chien Ho

Biochemistry 50 (34), 7350–7360, September 2011

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Posted in: Recent finds