Antagonists acting at the binding site

There are several strategies, but in theory we could design a drug (an antagonist) which would be the right shape to bind to the receptor site, but which would either fail to change the shape of the receptor protein or would distort it too much. Consider the following scenario. 

The compound shown in Fig. 5.20 fits the binding site perfectly and as a result does not cause any change of shape. Therefore, there is no biological effect and the binding site is blocked to the natural neurotransmitter. 

In such a situation, the antagonist has to compete with the agonist for the receptor, but usually the antagonist will get the better of this contest since it often binds more strongly. 

However, the recent advent of computer-based molecular graphics and the availability of X-ray crystallographic data now allow a more accurate representation of proteins and their binding sites (Chapter 7) and promise to spark off a new phase of drug development. 

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