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Study of protein–protein interactions by fluorescence of tryptophan analogs: Application to immunoglobulin G binding domain of streptococcal protein G
Author(s) -
Li Qi,
Du HaiNing,
Hu HongYu
Publication year - 2003
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10300
Subject(s) - chemistry , tryptophan , dissociation constant , fluorescence , protein g , immunoglobulin g , antibody , fluorescence anisotropy , biophysics , protein–protein interaction , plasma protein binding , biochemistry , amino acid , receptor , immunology , physics , quantum mechanics , membrane , biology
The protein–protein interaction system often contains many fluorophores that may significantly interfere with the quantitative determination of the binding abilities. To solve this perplexing problem, we biosynthetically incorporated the two tryptophan analogs, 5‐hydroxytryptophan and 7‐azatryptophan, into the immunoglobulin G (IgG) binding domain of streptococcal protein G (PGBD). The exclusive excitation and novel fluorescence changes in both the intensity and anisotropy are beneficial to reporting the details of the interactions between PGBD and the IgG fragments and enable assessment of the binding abilities. The dissociation constants are estimated to be 0.28 μ M for the binding of human Fc and 8.0 μ M for mouse Fc. The results clearly demonstrate that labeling of tryptophan analogs has very little effect on the binding abilities and is broadly applicable to quantitatively studying protein–protein interactions in a whole biomolecular complex. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 116–122, 2003