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Journal of Bacteriology, April 2000, p. 1995-2000, Vol. 182, No. 7
Department of Biology, Johns Hopkins
University, Baltimore, Maryland 21218
Received 20 September 1999/Accepted 12 January 2000
Full activation of transcription of the araFGH
promoter, pFGH, requires both the catabolite
activator protein (CAP) and AraC protein. At
pFGH, the binding site for CAP is centered at
position
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Cooperative Action of the Catabolite Activator
Protein and AraC In Vitro at the araFGH Promoter
and
41.5, an essential binding site for AraC is centered at
position
79.5, and a second, nonessential binding site is centered at position
154.5. In this work, we used the minimal promoter region required for in vivo activation of pFGH to
examine the roles of CAP and AraC in stimulating formation of open
complexes at pFGH. Migration retardation assays
of open complexes showed that RNA polymerase binds exceptionally
tightly to the AraC-CAP-pFGH complex and that
the order of addition of proteins to the initiating complex is
important. Similar assays with RNA polymerase containing truncated alpha subunits suggest that AraC interacts with the C-terminal domain
of the alpha subunit. Finally, AraC protein also acts to prevent the
improper binding of RNA polymerase at a pseudo promoter near the true
pFGH promoter.
*
Corresponding author. Mailing address: Department of
Biology, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218. Phone: (410) 516-5206. Fax: (410) 516-5213. E-mail:
bio_zrfs{at}jhuvms.hcf.jhu.edu.
Present address: Biology Department, Morgan State University,
Baltimore, MD 21251.
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