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Title:  'Gatekeeper' Protein is Key to Cellular Life -- TIPSHEETS
Date:    August 8, 2000





Media contact:                               Embargoed until 2 P.M. EDT
Cheryl Dybas                                 August 9, 2000
(703) 292-8070/cdybas@nsf.gov                 NSF PR 00-54

Program contact:
Eve Barak
(703) 292-8442/ebarak@nsf.gov

  "GATEKEEPER" PROTEIN IS KEY TO CELLULAR LIFE


     Researchers funded by the National Science Foundation (NSF)
and affiliated with Ohio State University have determined that a
seemingly ordinary protein called YidC found within the membranes
of bacteria serves as a gatekeeper of sorts, allowing into the
membranes other proteins essential for the bacteria to live.
When YidC isn't present, the bacteria dies.

     The finding surprised scientists who long believed that
certain "independent" proteins were able to pass into membranes
on their own. The new discovery, reported in this week's issue of
the journal Nature, may suggest a completely new pathway for the
translocation of proteins within basic biological units.

     While YidC has been known to be present in cells for some
time, researchers were unclear as to what role it might perform,
explained Ross Dalbey, a chemist at Ohio State University. Dalbey
and student James Samuelson were investigating the protein's role
in Escherichia coli bacteria as part of an NSF-supported study.
"The process of membrane insertion is needed for cellular
respiration in bacteria and mitochondria, as well as for
photosynthesis in chloroplasts," Dalbey said.

     The researchers hope that uncovering the function of YidC
and related proteins may offer new ways of either enhancing cell
function or in accelerating cell death - two mechanisms essential
in fighting most diseases. "In order to exploit cellular membranes
through biotechnology for the benefit of mankind, we need first to
understand the basic processes by which proteins are inserted into those
membranes," explains Eve Barak, program director in NSF's division of
molecular and cellular biosciences, which funded the research. "This
research sheds important new light on this fundamental biological
function."

     More startling was the discovery that several other proteins
that are remarkably similar to YidC may play similar roles inside
mitochondria and in chloroplasts as well.

     "Proteins are synthesized within the cytoplasm of the cell
but they then have to be transported, or inserted, either across
or into the membranes of organelles within the cell to do their
work," Dalbey said.  These membranes function as barriers, he
said, blocking proteins and other compounds from areas where they
don't belong.

     In their work, Dalbey and Samuelson developed a strain of E.
coli in which YidC can be depleted.  They found that when the
YidC was absent, proteins could not migrate into the membranes
and the bacteria died.

     They also looked at another specific protein called Procoat
that was considered "independent," that is, researchers believed
it would insert itself into the membrane on its own.  But in
bacteria lacking YidC,even the Procoat was blocked from entering
the membrane. "To everyone's surprise, the protein nearly
everybody thought inserted spontaneously requires YidC to succeed
in entering the membrane," Dalbey said.




    -NSF-