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Journal of Bacteriology, October 2003, p. 6215-6219, Vol. 185, No. 20
0021-9193/03/$08.00+0 DOI: 10.1128/JB.185.20.6215-6219.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
54-Dependent Activator DctD
Sungdae Park,2,
B. Tracy Nixon,2 and Timothy R. Hoover1*
Department of Microbiology, University of Georgia, Athens, Georgia,1 Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania2
Received 25 April 2003/ Accepted 29 July 2003
Activators of
54-RNA polymerase holoenzyme couple ATP hydrolysis to formation of an open promoter complex. DctD
1-142, a truncated and constitutively active form of the
54-dependent activator DctD from Sinorhizobium meliloti, displayed an altered DNase I footprint at its binding site located upstream of the dctA promoter in the presence of ATP. The altered footprint was not observed for a mutant protein with a substitution at or near the putative arginine finger, a conserved arginine residue thought to contact the nucleotide. These data suggest that structural changes in DctD
1-142 during ATP hydrolysis can be detected by alterations in the DNase I footprint of the protein and may be communicated by interactions between bound nucleotide and the arginine finger. In addition, kinetic data for changes in fluorescence energy transfer upon binding of 2'(3')-O-(N-methylanthraniloyl)-ATP (Mant-ATP) to DctD
1-142 and DctD suggested that these proteins undergo multiple conformational changes following ATP binding.
Present address: Bristol-Myers Squibb, Pharmaceutical Research Institute, Wallingford, CT 06492.
Present address: Department of Biochemistry and Molecular Biology, Medical College of Ohio, Toledo, OH 43614-5804.
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