7 Selected Examples of Drug Action at some Common Target Areas
7.1 Introduction
The action of drugs and the sites at which they are believed to act are very
varied. Common target sites are the cell envelopes and walls of microorganisms,
enzymes, receptors, nucleic acids and viruses. This chapter describes the struc-
tures and outlines the action of some of the drugs that target these sites. It also
outlines some of the general strategies adopted to discover new leads for some of
these targets.
7.2 Examples of drugs that disrupt cell membranes and walls
Cells are broadly classified as eithereukaryotesorprokaryotes(see Appendix 3).
Both types have a membrane, known as thecytoplasmicorplasma membrane
(see Appendix 3), that separates the internal medium (intracellular fluid) of the
cell from the external medium (extracellular fluid). Cytoplasmic membranes may
also divide the interior of a cell into separate compartments. In addition to the
cytoplasmic membrane, the more fragile membranes of plants and bacteria are
also protected by a rigid external covering known as a cell wall. The combin-
ation of cell wall and plasma membrane is referred to as thecell envelope
(Appendix 2).
The structure of a cytoplasmic membrane is complex (see Appendix 3). Built
into the membrane are receptors (see Appendix 4), enzymes (see Appendix 7)
Fundamentals of Medicinal Chemistry, Edited by Gareth Thomas
#2003 John Wiley & Sons, Ltd
ISBN 0 470 84306 3 (Hbk), ISBN 0 470 84307 1 (pbk)