隨著越來越多的膜表面受體被純化,其結構及轉導信號的方式逐步得以闡明。目前,按照受體的結構及其作用方式可將其分為三大類。這三大類受體在配體種類、受體的一般結構和功能及細胞對之發生反應的方式上有所不同,見表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 |
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