The effect of activating ligands on the intrinsic fluorescence of guanine nucleotide-binding regulatory proteins

T. Higashijima, K. M. Ferguson, P. C. Sternweis, E. M. Ross, M. D. Smigel, A. G. Gilman

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Abstract

The intensity of the tryptophan fluorescence of the α subunits of guanine nucleotide-binding regulatory proteins increases when they bind guanosine 5'-O-(3-thio)triphosphate (GTYγS). The kinetics of the fluorescence enhancement and of the measured binding of [35S]GTPγS are well correlated. The addition of Mg2+ to the nucleotide-bound proteins causes a further, rapid increase in the fluorescence intensity. Similar effects result from exposure of the proteins to F- and Mg2+, and the required concentration of F- is reduced by the inclusion of Al3+. It is presumed that the more highly fluorescent state of the G protein α subunits represents their active conformation.

Original languageEnglish (US)
Pages (from-to)752-756
Number of pages5
JournalJournal of Biological Chemistry
Volume262
Issue number2
Publication statusPublished - 1987

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ASJC Scopus subject areas

  • Biochemistry

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