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Proceedings Paper

Perturbations of the local environment of the single tyrosine residue in neurophysin upon ligand binding as determined by steady-state and time-resolved fluorescence quenching
Author(s): Carol A. Hasselbacher; Zhen Hai Shen; William R. Laws
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Paper Abstract

The neurophysins (NP) are proteins which function in neurohypophyseal peptide hormone transport and storage. We have been investigating the fluorescence properties of the single tyrosine residue (Tyr49) of bovine NPs. Since the intensity of Tyr49 fluorescence increases on ligand binding, measurements have been made with and without small peptides which bind at the hormone binding site. Steady-state iodide quenching produces Stern-Volmer plots with downward and upward curvature for NP and the NP:Phe-PheNH2 complex, respectively. Non-linear Stern-Volmer plots can result from multiple conformations of the solvated protein, multiple environments for the rotational isomers of the phenol side chain (rotamers), as well as from dynamic and static interactions of Tyr49 with the quencher. To help explain the steady-state data, time-resolved fluorescence quenching studies have been performed. Both NP and the NP:Phe-PheNH2 complex exhibit fluorescence intensity decays that can be fit by the sum of three exponentials that consist of the same time constants but with different weighting (amplitude) terms. With increasing [I-], the decay parameters for Tyr49 in NP are consistent with a multiple species model due to rotamers of Tyr49, the amplitudes are quencher independent and the lifetimes result in linear Stern-Volmer plots. The quenching studies on the NP:PhePheNH2 binary complex, however, cannot be analyzed in terms of a specific model because the fractional intensities of two of the exponential components are small.

Paper Details

Date Published: 1 April 1992
PDF: 9 pages
Proc. SPIE 1640, Time-Resolved Laser Spectroscopy in Biochemistry III, (1 April 1992); doi: 10.1117/12.58251
Show Author Affiliations
Carol A. Hasselbacher, Mount Sinai School of Medicine (United States)
Zhen Hai Shen, Mount Sinai School of Medicine (United States)
William R. Laws, Mount Sinai School of Medicine (United States)

Published in SPIE Proceedings Vol. 1640:
Time-Resolved Laser Spectroscopy in Biochemistry III
Joseph R. Lakowicz, Editor(s)

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