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Characterization of an alkaline transition intermediate stabilized in the Phe82Trp variant of yeast iso-1-cytochrome c
Zitatschlüssel ISI:000088491500040
Autor Rosell, F I and Harris, T R and Hildebrand, DP and Dopner, S and Hildebrandt, P and Mauk, A G
Seiten 9047-9054
Jahr 2000
ISSN 0006-2960
DOI 10.1021/bi001095k
Adresse 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Journal Biochemistry
Jahrgang 39
Nummer 30
Monat AUG 1
Zusammenfassung In general, mutation of the phylogenetically conserved residue Phe82 in yeast iso-1-cytochrome c destabilizes the native conformation of the protein by facilitating the ligand exchange reactions that are associated with the alkaline conformational transitions of the ferricytochrome. Of the Phe82 variants surveyed thus far, Phe82Trp is unique in that it adopts a thermodynamically stable, high-spin conformation at mildly alkaline pH. This species exhibits spectroscopic features that can only be detected transiently in other ferricytochromes c within the first 100 ms immediately after a pH-jump from neutrality to pH >10. Spectroscopic characterization of this high-spin reaction intermediate suggests that in addition to an obligatory pentacoordinate heme iron, a group within the heme pocket coordinates the heme iron but is then replaced either by Met80, to revert to the native conformation, or by Lys73 or Lys79, to yield one of the conventional alkaline conformers. Evidence is presented to suggest that this group is either a hydroxide ion or Tyr67 rather than a loosely bound Met80.
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