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Journal of Bacteriology, April 2000, p. 2119-2124, Vol. 182, No. 8
Department of Molecular Biology and
Biochemistry, Wesleyan University, Middletown, Connecticut 06459
Received 10 September 1999/Returned for modification 18 November
1999/Accepted 19 January 2000
Two Bacillus subtilis lysogenic libraries were probed
by an antibody specific for a previously described membrane-associated inhibitor of B. subtilis DNA replication (J. Laffan and W. Firshein, Proc. Natl. Acad. Sci. USA 85:7452-7456, 1988). Three clones
that reacted strongly with the antibody contained an entire open
reading frame. Sequencing identified one of the clones (R1-2) as
containing the E2 subunit of the pyruvate dehydrogenase complex,
dihydrolipoamide acetyltransferase. An AT-rich sequence in the origin
region was identified initially as the site to which extracts from the
R1-2 clone were bound. This sequence was almost identical to one
detected in Bacillus thuringiensis that also bound the E2
subunit but which was involved in activating the Cry1 protoxin gene of
the organism, not in inhibiting DNA replication (T. Walter and A. Aronson, J. Biol. Chem., 274:7901-7906, 1999). However, the exact
sequence was not as important in B. subtilis as the AT-rich
core region. Binding would occur as long as most of the AT character of
the core remained. Purified E2 protein obtained by use of PCR and an
expression vector reacted strongly with antibody prepared against the
repressor protein and the protein in the R1-2 clone, but its specificity for the AT-rich region was altered. The purified E2 protein
was capable of inhibiting membrane-associated DNA replication in vitro,
but anti-E2 antibody was variable in its ability to rescue repression
when added to the assay.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Probable Identification of a Membrane-Associated
Repressor of Bacillus subtilis DNA Replication as the E2
Subunit of the Pyruvate Dehydrogenase Complex
*
Corresponding author. Mailing address: Department of
Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06459.
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