JBC, Vol. 250, Issue 15, 5885-5889, Aug, 1975
Thermodynamics of complex formation between bovine liver glutamate dehydrogenase and analogs of ADP
S. Subramanian, D. C. Stickel and H. F. Fisher
A calorimetric study of the thermodynamic parameters for the binding of
adenosine, AMP, ADP, and ATP to L-glutamate dehydrogenase shows that the
variation of deltaG0 of binding is quite small and is correlated
qualitatively both with the effectiveness of these ribonucleotides as
activators of the L-glutamate dehydrogenase reaction and with size (for the
first three). Much larger variations are observed for the deltaH0 of
binding largely compensated by changes in deltaS0, with a zig-zag
dependence on the number of phosphate groups. For comparison, the binding
parameters are also obtained for the deoxyribose analogs of these compounds
as well as cyclic adenosine 3':5'-monophosphate and purine riboside. Salt
concentration and buffer composition were shown to affect mainly the
entropy changes for ADP binding; and the deltaCp values for binding of AMP
and ADP to the enzyme are quite small. It is suggested that the general
area of the enzyme surface which includes the binding sites for ADP and its
analogs contains a number of functional groups, each capable of an
energetically small interaction with some group on one or more of the
ligands, but so located that even the largest ligand cannot interact with
all of them simultaneously. Each ligand minimizes the free energy of the
system by selecting the best pattern of such individual interactions
permitted by its geometry. Such a pattern of microheterogeneity of
ligand-protein interactions may be a major source of the known specificity
of binding in biological systems.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?