Structural highlights
Function
[GYRB_ECOLI] DNA gyrase negatively supercoils closed circular double-stranded DNA in an ATP-dependent manner and also catalyzes the interconversion of other topological isomers of double-stranded DNA rings, including catenanes and knotted rings.[1] [2] [3]
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
Novobiocin is an antibiotic which binds to a 24 kDa fragment from the B subunit of DNA gyrase. Naturally occurring resistance arises from mutation of Arg-136 which hydrogen bonds to the coumarin ring of novobiocin. We have applied calorimetry to characterize the binding of novobiocin to wild-type and R136H mutant 24 kDa fragments. Upon mutation, the Kd increases from 32 to 1200 nM at 300 K. The enthalpy of binding is more favorable for the mutant (DeltaH degrees shifts from -12.1 to -17.5 kcal/mol), and the entropy of binding is much less favorable (TDeltaS degrees changes from -1.8 to -9.4 kcal/mol). Both of these changes are in the direction opposite to that expected if the loss of the Arg residue reduces hydrogen bonding. The change in heat capacity at constant pressure upon binding (DeltaCp) shifts from -295 to -454 cal mol-1 K-1. We also report the crystal structure, at 2.3 A resolution, of a complex between the R136H 24 kDa fragment and novobiocin. Although the change in DeltaCp often would be interpreted as reflecting increased burial of hydrophobic surface on binding, this structure reveals a small decrease. Furthermore, an ordered water molecule is sequestered into the volume vacated by removal of the guanidinium group. There are large discrepancies when the measured thermodynamic parameters are compared to those estimated from the structural data using empirical relationships. These differences seem to arise from the effects of sequestering ordered water molecules upon complexation. The water-mediated hydrogen bonds linking novobiocin to the mutant protein make a favorable enthalpic contribution, whereas the immobilization of the water leads to an entropic cost and a reduction in the heat capacity of the system. Such a negative contribution to DeltaCp, DeltaH degrees , and TDeltaS degrees appears to be a general property of water molecules that are sequestered when ligands bind to proteins.
The entropic penalty of ordered water accounts for weaker binding of the antibiotic novobiocin to a resistant mutant of DNA gyrase: a thermodynamic and crystallographic study.,Holdgate GA, Tunnicliffe A, Ward WH, Weston SA, Rosenbrock G, Barth PT, Taylor IW, Pauptit RA, Timms D Biochemistry. 1997 Aug 12;36(32):9663-73. PMID:9245398[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Noble CG, Maxwell A. The role of GyrB in the DNA cleavage-religation reaction of DNA gyrase: a proposed two metal-ion mechanism. J Mol Biol. 2002 Apr 26;318(2):361-71. PMID:12051843 doi:http://dx.doi.org/10.1016/S0022-2836(02)00049-9
- ↑ Sissi C, Chemello A, Vazquez E, Mitchenall LA, Maxwell A, Palumbo M. DNA gyrase requires DNA for effective two-site coordination of divalent metal ions: further insight into the mechanism of enzyme action. Biochemistry. 2008 Aug 19;47(33):8538-45. doi: 10.1021/bi800480j. Epub 2008 Jul, 22. PMID:18642932 doi:http://dx.doi.org/10.1021/bi800480j
- ↑ Schoeffler AJ, May AP, Berger JM. A domain insertion in Escherichia coli GyrB adopts a novel fold that plays a critical role in gyrase function. Nucleic Acids Res. 2010 Jul 31. PMID:20675723 doi:10.1093/nar/gkq665
- ↑ Holdgate GA, Tunnicliffe A, Ward WH, Weston SA, Rosenbrock G, Barth PT, Taylor IW, Pauptit RA, Timms D. The entropic penalty of ordered water accounts for weaker binding of the antibiotic novobiocin to a resistant mutant of DNA gyrase: a thermodynamic and crystallographic study. Biochemistry. 1997 Aug 12;36(32):9663-73. PMID:9245398 doi:http://dx.doi.org/10.1021/bi970294+
