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Journal of Bacteriology, March 2001, p. 1610-1620, Vol. 183, No. 5
Departments of
Bacteriology1 and
Biochemistry2 and the Center for
the Study of Nitrogen Fixation,3 University of
Wisconsin-Madison, Madison, Wisconsin 53706
Received 24 July 2000/Accepted 6 December 2000
Reversible ADP-ribosylation of dinitrogenase reductase, catalyzed
by the dinitrogenase reductase ADP-ribosyl transferase-dinitrogenase reductase-activating glycohydrolase (DRAT-DRAG) regulatory system, has
been characterized in Rhodospirillum rubrum and other
nitrogen-fixing bacteria. To investigate the mechanisms for the
regulation of DRAT and DRAG activities, we studied the heterologous
expression of R. rubrum draTG in Klebsiella
pneumoniae glnB and glnK mutants. In K. pneumoniae wild type, the regulation of both DRAT and DRAG activity appears to be comparable to that seen in R. rubrum. However, the regulation of both DRAT and DRAG activities
is altered in a glnB background. Some DRAT escapes
regulation and becomes active under N-limiting conditions. The
regulation of DRAG activity is also altered in a glnB
mutant, with DRAG being inactivated more slowly in response to
NH4+ treatment than is seen in wild type,
resulting in a high residual nitrogenase activity. In a
glnK background, the regulation of DRAT activity is similar
to that seen in wild type. However, the regulation of DRAG activity is
completely abolished in the glnK mutant; DRAG remains
active even after NH4+ addition, so there is no
loss of nitrogenase activity. The results with this heterologous
expression system have implications for DRAT-DRAG regulation in
R. rubrum.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.5.1610-1620.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Effect of PII and Its Homolog GlnK on
Reversible ADP-Ribosylation of Dinitrogenase Reductase by Heterologous
Expression of the Rhodospirillum rubrum Dinitrogenase
Reductase ADP-Ribosyl Transferase-Dinitrogenase
Reductase-Activating Glycohydrolase Regulatory System in
Klebsiella pneumoniae
*
Corresponding author. Mailing address: Department of
Bacteriology, University of Wisconsin-Madison, Madison, WI 53706. Phone: (608) 262-3567. Fax: (608) 262-9865. E-mail:
groberts{at}bact.wisc.edu.
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