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