Fast folding of cytochrome c

Michael M. Pierce, Barry T. Nall

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

Native iso-2 cytochrome c contains two residues (His 18, Met 80) coordinated to the covalently attached heme. On unfolding of iso-2, the His 18 ligand remains coordinated to the heme iron, whereas Met 80 is displaced by a non-native heme ligand, His 33 or His 39. To test whether non-native His-heme ligation slows folding, we have constructed a double mutant protein in which the non-native ligands are replaced by asparagine and lysine, respectively (H33N,H39K iso-2). The double mutant protein, which cannot form non-native histidine-heme coordinate bonds, folds significantly faster than normal iso-2 cytochrome c: τ = 14-26 ms for H33N,H39K iso-2 versus τ= 200 1,100 ms for iso-2. These results with iso-2 cytochrome c strongly support the hypothesis that non-native His-heme ligation results in a kinetic barrier to fast folding of cytochrome c. Assuming that the maximum rate of a conformational search is about 1011 s-1 the results imply that the direct folding pathway of iso-2 involves passage through on the order of 109 or fewer partially folded conformers.

Original languageEnglish (US)
Pages (from-to)618-627
Number of pages10
JournalProtein Science
Volume6
Issue number3
DOIs
StatePublished - Mar 1997

Keywords

  • histidine
  • iso-2 cytochrome c
  • non-native heme ligands
  • protein folding
  • yeast

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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