http://dailynews.yahoo.com/headlines/hl/story.html?s=v/nm/19980925/hl/get8_1.html
Cell's ``recycling'' may yield clues to aging
NEW YORK, Sep 25, 1998 (Reuters) -- Scientists have identified a
whirling 'dervish-like' structure within cells that helps to recycle
existing compounds into ATP, the molecule that stores the energy needed
for life. They believe the discovery could point to new methods of
slowing the aging process.
The structure is ``one of the most complex molecules ever revealed,''
said Dr. Peter Pedersen, a researcher at Johns Hopkins University in
Baltimore, Maryland, and co-author of a study published in the September
issue of the Proceedings of the National Academy of Sciences.
Scientists have long understood that cellular energy production occurs
in the mitochondria, capsule-shaped 'power plants' found in the cell.
Still, the exact mechanisms behind this process have remained unclear.
The Johns Hopkins team believe that they may have cleared up some of
that mystery. They focused their efforts on tiny, mushroom-shaped
molecules found within the mitochondria. These molecules are enzymes
called adenosine triphosphate synthase, which make ATP.
The ATP synthase enzyme is a relatively complex structure ''almost six
times larger than the blood molecule hemoglobin,'' Pedersen explained.
Examination of ATP in rat liver cells revealed that the 'stem' portion
of the mushroom-shaped molecule revolves, dervish-like, under the 'cap.'
As the stem rotates, it creates enough energy to turn on the
ATP-synthesis 'factory' located within the cap. The ingredients
necessary for the formation of ATP are constantly recycled within this
cap, according to the study authors. When ATP synthesis is complete, the
cap disengages from the stem, allowing ATP to be used as an
energy source within the cell.
The recycling of ATP helps explain the body's ability to function
without an enormous daily intake of food. Without this recycling
process, ``people would have to produce more than half their body weight
in ATP every day to meet their energy needs,'' Pedersen explained.
He noted that ``free-radicals'' -- the negative byproducts of metabolism
-- could potentially damage ATP synthesis at the molecular level.
Scientists have long believed that the gradual accumulation of free
radical damage within cells plays a key in both disease formation and
the aging process. ``If ATP synthase is a site of free radical
damage,'' Pedersen speculated, ``that could explain why we become less
energetic with age.''
Antioxidant compounds (including vitamins C and E) are thought to 'mop
up' free-radicals and improve cellular health. Pedersen said that a
better understanding of the cell's energy production systems could
someday help researchers develop agents that could repair damage caused
by free radicals. ``Now that we know the molecular structures (involved
in energy production), we can pinpoint damaged regions if they occur,''
he explained.
SOURCE: Proceedings of the National Academy of Sciences
1998;95:11605-11070.
Copyright © 1998 Reuters Limited.
--
Judith Richards, London, Ontario, Canada
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