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J Bacteriol, May 1998, p. 2484-2492, Vol. 180, No. 9
Division of Bacterial Products, Center for
Biologics Evaluation and Research, Food and Drug Administration,
Bethesda, Maryland 20892
Received 19 August 1997/Accepted 19 February 1998
The effects of short deletions of the C terminus of the BvgA
response regulator protein of the BvgAS two-component system were
examined in Bordetella pertussis. When present as a single copy in the chromosome, deletions removing as few as two amino acids
conferred a completely Bvg
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Mutations Affecting the
Subunit of
Bordetella pertussis RNA Polymerase Suppress Growth
Inhibition Conferred by Short C-Terminal Deletions of the Response
Regulator BvgA
phenotype. When provided in
trans, on the broad-host-range plasmid pRK290, under the
control of the native bvgAS promoter, deletions of two or
three amino acids conferred a profound growth inhibition which was
dependent on the integrity and activity of the wild-type chromosomal
bvgAS locus. It is proposed that this phenotype was the
result of an inappropriate interaction of the mutant BvgA protein with
the RNA polymerase enzyme, specifically the
subunit. Mutant strains
in which this growth inhibition was relieved were isolated and
characterized. Although most of the suppressor mutations affected
either the mutant plasmid copy or the wild-type chromosomal bvg locus, three mutations which affected the
subunit
of B. pertussis RNA polymerase were also isolated. Two of
these resulted in increased levels of the
subunit, and one caused a
substitution of glycine for the aspartic acid residue at position 171, in the N-terminal domain. All three mutations also resulted in a
differential phenotype in that expression of fha was
essentially normal, but expression of ptx was greatly
reduced.
*
Mailing address: Division of Bacterial Products, Center
for Biologics Evaluation and Research, Food and Drug Administration, 8800 Rockville Pike, Bethesda, MD 20892. Phone: (301) 496-1785. Fax:
(301) 402-2776. E-mail: stibitz{at}helix.nih.gov.
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