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Title
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Conserved polar residues in the transmembrane domain of the human tachykinin receptor : functional roles and structural implications
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Author
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Abstract
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| We have studied the effects of agonist and antagonist binding, agonist-induced activation and agonist-induced desensitization of the human tachykinin NK2 receptor mutated at polar residues Asn-51 [in transmembrane helix 1 (TM1)], Asp-79 (TM2) and Asn-303 (TM7), which are highly conserved in the transmembrane domain in the rhodopsin family of G-protein-coupled receptors. Wild-type and mutant receptors were expressed in both COS-1 cells and Xenopus oocytes. The results show that the N51D mutation results in a receptor which, in contrast with the wild-type receptor, is desensitized by the application of a concentration of 1 mu M of the partial agonist GR64349, indicating that the mutant is more sensitive to agonist activation than is the wild-type receptor. In addition, we show that, whereas the D79E mutant displayed activation properties similar to those of the wild-type receptor, the D79N and D79A mutants displayed a severely impaired ability to activate the calcium-dependent chloride current. This suggests that it is the negative charge at Asn-79, rather than the ability of this residue to hydrogen-bond, that is critical for the activity of the receptor. Interestingly, the placement of a negative charge at position 303 could compensate for the removal of the negative charge at position 79, since the double mutant D79N/N303D displayed activation properties similar to those of the wild-type receptor. This suggests that these two residues are functionally coupled, and may even be in close proximity in the three-dimensional structure of the human tachykinin NK2 receptor. A three-dimensional model of the receptor displaying this putative interaction is presented. |
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Language
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English
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Source (journal)
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The biochemical journal. - London, 1984, currens
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Publication
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London
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1999
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ISSN
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0264-6021
[print]
1470-8728
[online]
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DOI
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10.1042/0264-6021:3390055
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Volume/pages
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339
:1
(1999)
, p. 55-61
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ISI
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000079702300008
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Full text (Publisher's DOI)
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Full text (publisher's version - intranet only)
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