"From the standpoint of hemoglobin biology, this finding represents a new function and a novel mechanism for Ascaris hemoglobin," she said. "In bacteria, hemoglobin's function is detoxification, while in mammals, its function is respiration. In Ascaris, at the evolutionary divide, we see the evolution of the 'functional switch' -- respiratory function (control of oxygen) and the detoxification function (removal of oxygen) are the same. And all is controlled by NO."
Minning's work in Ascaris biology was conducted in the laboratory of Dr. Daniel Goldberg, a Washington University microbiologist and HHMI investigator. The keys to hemoglobin's evolution, the researchers believe, are the chemical reactions that take place between hemoglobin, oxygen and NO, a ubiquitous chemical involved in many life processes. These findings suggest that contrary to commonly held beliefs, hemoglobin has evolved over millions of years in response to NO, and not oxygen.
"More than a billion years ago, the atmosphere on Earth contained NO, and not oxygen," Stamler explained. "So the early development of hemoglobin in bacteria and other microbes could not have been for the delivery of oxygen, but instead was for the detoxification of NO. On the evolutionary tree, the Ascaris worm sits right at the point where bacteria branches off one way and man in another," he said.
"We've known that hemoglobin in Ascaris binds oxygen 25,000 times more
tightly than human hemoglobin -- the tightest that oxygen is held by any
molecule," Minning said. "It's been a mystery why a hemoglobin that is supposed
to deliver oxygen would bind it so tightly that oxygen could never be released,
a mystery that ha
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Contact: Richard Merritt
Merri@mc.duke.edu
919-684-4148
Duke University Medical Center
29-Sep-1999