Structure of protein collagen seen at unprecedented level of detail
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ARGONNE, Ill. (Feb. 22, 2008) — The structure and behavior of one of
the most common proteins in our bodies has been resolved at a level of
detail never before seen, thanks to new research performed at the Advanced
Photon Source (APS) at the U.S. Department of Energy's Argonne National Laboratory.
The Advanced Photon Source, located at Argonne National Laboratory,
is funded by the U.S. Department of Energy's Office of Basic
Energy Sciences as part of its mission to foster and support fundamental research to
expand the scientific foundations for new and improved energy technologies
and for understanding and mitigating the environmental impacts of energy
use. |
Illinois Institute of Technology biologist Joseph Orgel used the high-energy
X-rays produced by the APS to examine the structure of collagen, a protein
that composes more than a quarter of all protein in the human body and forms
the principal component of skin, teeth, ligaments, the heart, blood vessels,
bones and cartilage. In these tissues, collagen molecules pack themselves into
overlapping bundles called fibrils. These fibrils, which each contain billions
of atoms, entwine themselves into collagen fibers that are visible to the naked
eye.
Scientists have known the basic molecular structure of collagen since the
1950s, when several different international groups of scientists discovered
that it had a triple-stranded helical structure. However, researches had never
before had the ability to study the structure of an entire fibril in the same
way that they could study an individual collagen molecule, according to Orgel.
Orgel and his team performed diffraction studies on intact collagen fibrils
inside the tendons of rat tails in order to understand just how the protein
functioned within unbroken tissue. "We tried to draw a highly accurate
map of the molecular structure of tissues," Orgel said. "By doing
so, we hope to transform a very basic understanding that we have of the molecular
structure of tissue into a much more tangible form."
Since the scientists kept the tendon tissue intact, they could see how the
collagen molecule binds to collagenases, a class of enzymes which when working
properly help to regulate the normal growth and development of animals but
when malfunctioning can lead to the metastasis of cancerous tumors or rheumatoid
arthritis. The visualization of this interaction could help drug developers
to create an inhibitor to prevent the pathological action of the enzyme, Orgel
said.
Previous studies of the structure of collagen had looked only at crystals
of small fragments of the protein, so scientists had little idea of how it
looked within intact tissue. "It's impossible to get the information that
we did by removing tiny chunks of the tissue," Orgel said. "We couldn't
obtain this data by single-crystal crystallography. This research was made
possible only because of the BioCAT beamline
provided by the APS."
The research appears in the February 26 issue of the Proceedings
of the National Academy of Sciences, and is available online at http://www.pnas.org/cgi/reprint/0710588105v1.
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Department of Energy's Office
of Science.
By Jared Sagoff.
For more information, please contact Steve McGregor
(630/252-5580 or media@anl.gov)
at Argonne.
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