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The Additional 165 Amino Acids in the B Protein of Escherichia coli DNA Gyrase Have an Important Role in DNA Binding

Chatterji, Monalisa and Unniraman, Shyam and Maxwell, Anthony and Nagaraja, Valakunja (2000) The Additional 165 Amino Acids in the B Protein of Escherichia coli DNA Gyrase Have an Important Role in DNA Binding. In: Journal of Biological Chemistry, 275 (20). pp. 22888-22894.


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DNA gyrase is the only enzyme known to negatively super coil DNA. The enzyme is a heterotetramer of A2B2 subunit composition. Alignment of the primary sequence of gyrase B (GyrB) from various species shows that they can be grouped into two classes. The GyrB of Gram-negative eubacteria has a stretch of about 165 amino acids in the C-terminal half, which is lacking in other GyrB subunits and type II topoisomerases. In Escherichia coli, no function has so far been attributed to this stretch. In this study, we have tried to assess the function of this region both in vivo and in vitro. A deletant (GyrBD160) lacking this region is non-functional in vivo. The holoenzyme reconstituted from gyrase A (GyrA) and GyrBD160 shows reduced but detectable supercoiling and quinolone-induced cleavage activity in vitro. GyrBD160 retains its ability to bind to GyrA and novobiocin. However, when reconstituted with GyrA, the deletant shows greatly impaired DNA binding. The intrinsic ATPase activity of the GyrBD160 is comparable to that of wild type GyrB, but this activity is not stimulated by DNA. These studies indicate that the additional stretch present in GyrB is essential for the DNA binding ability of E.coli gyrase.

Item Type: Journal Article
Publication: Journal of Biological Chemistry
Publisher: The American Society for Biochemistry and Molecular Biology,
Keywords: DNA Binding;DNA Gyrase;topoisomerases
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 16 Jul 2004
Last Modified: 19 Sep 2010 04:14
URI: http://eprints.iisc.ac.in/id/eprint/1059

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