Receptors for adrenergic amines, serotonin, acetylcholine (muscarinic
but not nicotinic), many peptide hormones, odorants, and even visual receptors (in retinal rod and
cone cells) all belong to the serpentine family. The amino and carboxyl terminals of each of these
receptors are located on the extracellular and cytoplasmic sides of the membrane, respectively.
Different serpentine receptors resemble one another rather closely in amino acid sequences and in
the locations of their hydrophobic transmembrane regions and hydrophilic extra- and intracellular
loops, suggesting that all were derived from a common evolutionary precursor.
Last updated 8/13/03
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