Primary structure of the human kidney a2-adrenoceptor. The amino acid sequence is represented by the one-letter code. (Reprinted with permission from Regan JW et al. Cloning and expression of a human kidney cDNA. Proc Natl Acad Sci USA 85:6301, 1988.)

The variety of possible responses is further increased by the fact that receptor-coupled G proteins can either activate enzymes other than adenylate cyclase or can directly influence ion channel functions.

Many different receptor types are coupled to G proteins, including receptors for norepinephrine and epinephrine (a- and (3-adrenoceptors), 5-hydroxytrypta-mine (serotonin or 5-HT receptors), and muscarinic acetylcholine receptors. Figure 2.1 presents the structure of one of these, the a2-adrenoceptor from the human kidney. All members of this family of G protein-coupled receptors are characterized by having seven membrane-enclosed domains plus extracellular and intracellular loops. The specific binding sites for agonists occur at the extracellular surface, while the interaction with G proteins occurs with the intracellular portions of the receptor. The general term for any chain of events initiated by receptor activation is signal trans-duction.

Was this article helpful?

0 0
How To Bolster Your Immune System

How To Bolster Your Immune System

All Natural Immune Boosters Proven To Fight Infection, Disease And More. Discover A Natural, Safe Effective Way To Boost Your Immune System Using Ingredients From Your Kitchen Cupboard. The only common sense, no holds barred guide to hit the market today no gimmicks, no pills, just old fashioned common sense remedies to cure colds, influenza, viral infections and more.

Get My Free Audio Book

Post a comment