Structural features of cytochrome c' folding intermediates revealed by fluorescence energy-transfer kinetics.

• We employed fluorescence energy-transfer probes to investigate the polypeptide dynamics accompanying cytochrome c' folding. Analysis of fluorescence energy-transfer kinetics from wild-type Trp-72 or Trp-32 in a crystallographically characterized (1.78 A) Q1A/F32W/W72F mutant shows that there is structural heterogeneity in denatured cytochrome c'. Even at guanidine hydrochloride concentrations well beyond the unfolding transition, a substantial fraction of the polypeptides ( approximately 50%) adopts compact conformations (tryptophan-to-heme distance, approximately 25 A) in both pseudo-wild-type (Q1A) and mutant proteins. A burst phase (< or =5 ms) is revealed when stopped flow-triggered refolding is probed by tryptophan intensity: measurements on the Q1A protein show that approximately 75% of the Trp-72 fluorescence (83% for Trp-32) is quenched within the mixing deadtime, suggesting that most of the polypeptides have collapsed.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

NATURVETENSKAP  -- Kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences (hsv//eng)

Nyckelord

Amino Acids

analysis

Bacterial Proteins

chemistry

metabolism

Crystallography

X-Ray

methods

Cytochromes c1

chemistry

metabolism

Energy Transfer

Guanidine

Kinetics

Protein Conformation

Protein Folding

Saccharomyces cerevisiae

Saccharomyces cerevisiae Proteins

chemistry

metabolism

Spectrometry

Fluorescence

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)