Primary structural homology between the hormone binding site of the LH
/CG receptor and the enzyme binding site of chymotrypsin inhibitor has
been identified. This has led to the application of a knowledge-based
approach of molecular modelling to describe the interaction of chorio
gonadotropin (CG) with the LH/CG receptor. A tertiary structural model
for the mode of recognition between the hormone and the receptor has
been proposed. As in other such processes at the molecular level, the
recognition between CG and its receptor is mediated through non-covale
nt interactions. The specificity of recognition is achieved by complem
entarity in van der Waals surfaces, hydrogen bonding and non-polar ass
ociations. The model shows nine hydrogen bonds between the hormone and
the receptor involving polar side chains as well as backbone amine an
d carbonyl groups. A hydrophobic cluster involving side chain groups a
t the interface is also important in stabilization of the intermolecul
ar interactions.