Folding of Yeast Iso-1-AM Cytochrome c

Efrain H. Zuniga, Barry T. Nall

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


We describe a specific modification of iso-1 cytochrome c which results in blocking a single free sulfhydryl group. The derivative differs from the unmodified protein by the introduction of a small, uncharged group, thus maintaining the same charge balance as the native protein. The modified protein, obtained by treatment of iso-1 cytochrome c with iodoacetamide, has an activity indistinguishable from that of the unmodified protein in the lactate dehydrogenase-cytochrome c reductase system from yeast and has the same stability toward denaturation by guanidine hydrochloride. The kinetics of fluorescence changes associated with the guanidine hydrochloride induced folding-unfolding transition for modified iso-1 cytochrome c (iso-1-AM) have been investigated throughout the transition zone by using stopped-flow mixing. The results are compared to those for the yeast isozyme, iso-2 cytochrome c. The main features of the fluorescence-detected folding kinetics are similar, as might be expected for homologous proteins; however, the limiting value of the fraction of fast refolding protein (α2) below the transition zone is smaller for iso-1-AM (∼0.7) than for iso-2 (∼0.9).

Original languageEnglish (US)
Pages (from-to)1430-1437
Number of pages8
Issue number6
StatePublished - 1983
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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