随着越来越多的膜表面受体被纯化，其结构及转导信号的方式逐步得以阐明。目前，按照受体的结构及其作用方式可将其分为三大类。这三大类受体在配体种类、受体的一般结构和功能及细胞对之发生反应的方式上有所不同，见表21－2。
Table 21－2 Classification of MembraneReceptors:Characteristics of Three Groups of Receptors
| Characteristics | Ion Channel Receptors | G-Protein-Linked receptors | Recetpors with a Single Transmembrane Domain |
| Endogenous ligands | Neurotransmitter | Neurotransmitter | Growth factor hormone |
| | Hormone | Cytokine |
| | Auloacoid | |
| | Chemotactic factor | |
| | Exogenous stimulant | |
| Structure | Oligomer with a pore | Probably monomer | Monomer of oligoner |
| | | with (±）catalytic |
| | | domain |
| Number of transmem | Four per subunit | Seven | One per subunit |
| bane segments | | | |
| Function | Ion channel | Activation of G proteins | Tyrosine kinase |
| | | Giuanylate cyclase(?) |
| Cellular responses | Depolarization or | Depolarization or | Regulation of function |
| hyperpolarization | hyperpolarization | and expression of |
| | Regulation of function | proteins |
| | and expression of | Proliferation or |
| | proteins | differentiation |
膜受体介导的信号转导 | 膜受体信号转导的分子机理 