Fast amide proton exchange reveals close relation between native-state dynamics and unfolding kinetics.
It has long been recognized that many proteins fold and unfold via partially structured intermediates, but it is still unclear why some proteins unfold in a two-state fashion while others do not. Here we compare the unfolding pathway of the small one-domain protein barstar with its dynamics under native conditions. Using very fast proton-exchange experiments, extensive dynamic heterogeneity within the native-state ensemble could be identified. Especially the dynamics of helix 3, covering the hydrophobic core of the molecule, is found to be clearly cooperative but decoupled from the global dynamics. Moreover, an initial unfolding of this helix followed by the breakdown of the remaining tertiary structure can be concluded from the comparison of the proton exchange experiments with unfolding kinetics detected by stopped-flow fluorescence. We infer that the unfolding pathway of barstar is closely coupled to its native-state dynamics.
Hofmann
Hagen
H
Institute of Biochemistry and Biotechnology, Institute of Physics, Biophysics group and Mitteldeutsches Zentrum für Struktur and Dynamik der Proteine (MZP), Martin-Luther University Halle-Wittenberg, 06099 Halle.
Weininger
Ulrich
U
Löw
Christian
C
Golbik
Ralph P
RP
Balbach
Jochen
J
Ulbrich-Hofmann
Renate
R
D000577:Amides / Q000737:chemistry*; D007700:Kinetics; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D013050:Spectrometry, Fluorescence / Q000379:methods; D013816:Thermodynamics
D000577:Amides; D011506:Proteins; D011522:Protons