Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
May 09, 2005
Physics Prof Finds Old-Fashioned Energy Source in Unlikely Places
A University of Guelph biophysics professor has found that a primitive “energy-making” pathway has unexpectedly survived in more advanced organisms, a discovery that may shed new light on how humans and other animals tell night from day.
The research by Leonid Brown on rhodopsins — a class of proteins with seemingly night-and-day roles in different organisms — recently appeared in Proceedings of the National Academy of Sciences and in subsequent articles in Science Now and The Scientist.
“What is exciting is using our knowledge of bacterial rhodopsins to get some new information about other organisms, not just bacteria, and to figure out new functions,” he said.
In bacteria and related prokaryotes lacking a distinct nucleus, bacteriorhodopsin proteins run a pump that turns light into chemical energy. In eukaryotes — including fungi, green plants and animals that get their energy from photosynthesis or respiration — rhodopsins have been harnessed to work as light receptors of varying sophistication.
Fungi may be higher life forms than bacteria, but they are not above borrowing a microbial trick for making energy, said Brown, who began studying these proteins about 15 years ago for his undergraduate degree at Moscow State University. He recently found a form of fungal rhodopsin that looked more like the bacterial protein. When he isolated and tested the fungal protein — by shining light on artificial membranes containing the rhodopsin in his Guelph lab — he found its action also mimicked bacterial activity. This energy-generating “proton pump” has never before been seen outside of prokaryotes.
Brown and his collaborators hope to learn more about the protein, including why a primitive energy-making pathway is still at work in a more advanced kingdom of living things. They also believe they’ll be able to trace that microbial energy pump among other higher — albeit still relatively humble — life forms.
As in other animals, humans have rhodopsins, or light-sensitive pigments, in the retina that tell the brain when the eye has detected light. And although the same kinds of proteins gave up their energy-making power long before they took on new light-sensing duties in the human eye, Brown believes his work with bacterial rhodopsins may help people understand how animals use melanopsin to distinguish day from night. He’s also interested in investigating how rhodopsins work in other organisms, from other fungi to algae to humans.