pH-induced conformational changes in spinach ferredoxin

Steady-state and time-resolved fluorescence studies

Jan Kieleczawa, Louisa L. France, John C. Sutherland, Geoffrey Hind

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Steady-state and time-resolved fluorescence techniques were used to monitor pH-induced conformational changes in spinach ferredoxin. An increase was seen in the wave-length maximum of tryptophan-73 (Trp-73) emission, from 325 nm below pH 6.0 to 342 nm above pH 7.0, indicating significantly diminished hydrophobicity, at pH 7.0, in the environment of the indole ring. Raising the solution pH from 6.0 to 7.6 also decreased the binding of the detergent Brij-96, showing that the ferredoxin molecule as a whole became more hydrophilic at higher pH. Nonionic (acrylamide) and ionic (I- and Cs+) quenchers were used to probe the tryptophan environment. Trp-73 is partially shielded from I-, presumably by negatively charged residues, as predicted from the amino acid sequence and three-dimensional structure of plant-type ferredoxins. Ionic strength and pH effects on tryptophan fluorescence lifetimes follow a pattern common to single-tryptophan proteins: the emission decays can be fit to a biexponential model in which the lifetime of the excited state increases with increasing pH. The indication of a pH-induced conformational change in the range pH 6.0 to 7.6 is discussed with reference to the physiological association of ferredoxin with ferredoxin:NADP+ oxidoreductase and the rise in chloroplast stromal pH in the light.

Original languageEnglish (US)
Pages (from-to)63-69
Number of pages7
JournalArchives of Biochemistry and Biophysics
Volume298
Issue number1
DOIs
StatePublished - Jan 1 1992
Externally publishedYes

Fingerprint

Ferredoxins
Spinacia oleracea
Tryptophan
Fluorescence
Ferredoxin-NADP Reductase
pH effects
Acrylamide
Hydrophobicity
Ionic strength
Excited states
Detergents
Association reactions
Amino Acids
Wavelength
Molecules
Plant Structures
Chloroplasts
Hydrophobic and Hydrophilic Interactions
Osmolar Concentration
Proteins

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

Cite this

pH-induced conformational changes in spinach ferredoxin : Steady-state and time-resolved fluorescence studies. / Kieleczawa, Jan; France, Louisa L.; Sutherland, John C.; Hind, Geoffrey.

In: Archives of Biochemistry and Biophysics, Vol. 298, No. 1, 01.01.1992, p. 63-69.

Research output: Contribution to journalArticle

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