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Title: Binding of oxytocin and 8-arginine-vasopressin to neurophysin studied by /sup 15/N NMR using magnetization transfer and indirect detection via protons

Abstract

NMR was used to monitor the binding to neurophysin of oxytocin and 8-arginine-vasopressin, /sup 15/N labeling being used to identify specific backbone /sup 15/N and /sup 1/H signals. The most significant effects of binding were large downfield shifts in the amino nitrogen resonance of Phe-3 of vasopressin and in its associated proton, providing evidence that the peptide bond between residues 2 and 3 of the hormones is hydrogen-bonded to the protein within hormone-neurophysin complexes. Suggestive evidence for hydrogen bonding of the amino nitrogen of Tyr-2 was also obtained in the form of decreased proton exchange rates on binding; however, the chemical shift changes of this nitrogen and its associated proton indicated that such hydrogen bonding, if present, is probably weak. Shifts in the amino nitrogen of Asn-5 and in the -NH protons of both Asn-5 and Cys-6 demonstrated that these residues are significantly perturbed by binding, suggesting conformational changes of the ring on binding and/or the presence of binding sites on the hormone outside the 1-3 region. No support was obtained for the thesis that there is a significant second binding site for vasopressin on each neutrophysin chain. The behavior of both oxytocin and vasopressin on binding was consistent withmore » formation of 1:1 complexes in slow exchange with the free state under most pH conditions. At low pH there was evidence of an increased exchange rate. Additionally, broadening of /sup 15/N resonances in the bound state at low pH occurred without a corresponding change in the resonances of equilibrating free hormone. The results suggest significant conformational alteration in neurophysin-hormone complexes at low pH possibly associated with protonation of the carboxyl group of the hormone-protein salt bridge.« less

Authors:
;
Publication Date:
Research Org.:
Rockefeller Univ., New York, NY
OSTI Identifier:
5400501
Alternate Identifier(s):
OSTI ID: 5400501
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemistry; (United States); Journal Volume: 26:20
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; OXYTOCIN; CONFIGURATION INTERACTION; NUCLEAR MAGNETIC RESONANCE; PROTEINS; VASOPRESSIN; ARGININE; CHEMICAL SHIFT; NITROGEN 15; NMR SPECTRA; OVERHAUSER EFFECT; PH VALUE; PROTONS; AMINO ACIDS; BARYONS; CARBOXYLIC ACIDS; ELEMENTARY PARTICLES; FERMIONS; HADRONS; HORMONES; ISOTOPES; LIGHT NUCLEI; MAGNETIC RESONANCE; NITROGEN ISOTOPES; NUCLEI; NUCLEONS; ODD-EVEN NUCLEI; ORGANIC ACIDS; ORGANIC COMPOUNDS; PEPTIDE HORMONES; PITUITARY HORMONES; RESONANCE; SPECTRA; STABLE ISOTOPES 550601* -- Medicine-- Unsealed Radionuclides in Diagnostics

Citation Formats

Live, D.H., and Cowburn, D. Binding of oxytocin and 8-arginine-vasopressin to neurophysin studied by /sup 15/N NMR using magnetization transfer and indirect detection via protons. United States: N. p., 1987. Web.
Live, D.H., & Cowburn, D. Binding of oxytocin and 8-arginine-vasopressin to neurophysin studied by /sup 15/N NMR using magnetization transfer and indirect detection via protons. United States.
Live, D.H., and Cowburn, D. Tue . "Binding of oxytocin and 8-arginine-vasopressin to neurophysin studied by /sup 15/N NMR using magnetization transfer and indirect detection via protons". United States. doi:.
@article{osti_5400501,
title = {Binding of oxytocin and 8-arginine-vasopressin to neurophysin studied by /sup 15/N NMR using magnetization transfer and indirect detection via protons},
author = {Live, D.H. and Cowburn, D.},
abstractNote = {NMR was used to monitor the binding to neurophysin of oxytocin and 8-arginine-vasopressin, /sup 15/N labeling being used to identify specific backbone /sup 15/N and /sup 1/H signals. The most significant effects of binding were large downfield shifts in the amino nitrogen resonance of Phe-3 of vasopressin and in its associated proton, providing evidence that the peptide bond between residues 2 and 3 of the hormones is hydrogen-bonded to the protein within hormone-neurophysin complexes. Suggestive evidence for hydrogen bonding of the amino nitrogen of Tyr-2 was also obtained in the form of decreased proton exchange rates on binding; however, the chemical shift changes of this nitrogen and its associated proton indicated that such hydrogen bonding, if present, is probably weak. Shifts in the amino nitrogen of Asn-5 and in the -NH protons of both Asn-5 and Cys-6 demonstrated that these residues are significantly perturbed by binding, suggesting conformational changes of the ring on binding and/or the presence of binding sites on the hormone outside the 1-3 region. No support was obtained for the thesis that there is a significant second binding site for vasopressin on each neutrophysin chain. The behavior of both oxytocin and vasopressin on binding was consistent with formation of 1:1 complexes in slow exchange with the free state under most pH conditions. At low pH there was evidence of an increased exchange rate. Additionally, broadening of /sup 15/N resonances in the bound state at low pH occurred without a corresponding change in the resonances of equilibrating free hormone. The results suggest significant conformational alteration in neurophysin-hormone complexes at low pH possibly associated with protonation of the carboxyl group of the hormone-protein salt bridge.},
doi = {},
journal = {Biochemistry; (United States)},
number = ,
volume = 26:20,
place = {United States},
year = {Tue Oct 06 00:00:00 EDT 1987},
month = {Tue Oct 06 00:00:00 EDT 1987}
}