Dh. Williams et al., FUNCTIONAL ROLES OF NATURAL-PRODUCTS - THE INVOLVEMENT OF EXTENDED ARRAYS OF WEAK-INTERACTIONS IN COOPERATIVE BINDING PHENOMENA, Pure and applied chemistry, 66(10-11), 1994, pp. 1975-1982
A factorisation of the free energy of binding into various ''costs'' a
nd ''benefits'' has provided the basis for a semi-quantitation of some
weak interactions in solution. It has become clear that the entropic
cost of motional restriction on binding (A + B --> A.B) increases with
increasing exothermicity of the association; this exothermicity must
of course reflect not only interactions at the interface between A and
B, but also the change in bonding throughout B (if B represents the r
eceptor). We illustrate cooperativity and anti-cooperativity by refere
nce to effects of ligand binding (as models of classical agonists and
antagonists) on the dimerisation of vancomycin-group antibiotics. Sinc
e dimerization of receptors (promoted by ligand binding) is a common t
heme in biological signalling, it must presumably have an advantage in
natural selection. We suggest that concurrent demands of ligand bindi
ng and receptor dimerization may permit a more specific control of tho
se ligand structures which can cause signal transmission. In this way,
specificity in biological signalling might be aided.