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Mutational analysis of the human vasoactive intestinal peptide receptor subtype VPAC2: role of basic residues in the second transmembrane helix
Effects of specific charged parts in the second membrane segment on the human VPAC2 receptor function
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Abstract
Vasoactive intestinal polypeptide (VIP) activated VPAC(2) receptors with an EC(50) value of 7 nM, compared to much higher values at mutated receptors.
- Basic residues arginine 172 (R172) and lysine 179 (K179) in the VPAC(2) receptor may play a role in receptor recognition and activation.
- Mutations at R172 and K179 resulted in significantly higher EC(50) values, indicating reduced receptor activation by VIP.
- The VPAC(2)-selective VIP analogue [hexanoyl-His(1)]-VIP (C(6)-VIP) showed higher affinity and efficacy compared to VIP at mutated receptors.
- Asn(3)-VIP and Gln(3)-VIP acted as partial agonists at the wild type receptor but were more effective than VIP at the R172Q and R172L mutated receptors.
- Lower affinities for all tested agonists were observed at the K179I and K179Q mutated receptors compared to wild-type receptors.
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