The earliest events in protein folding: Helix dynamics in proteins and model peptides
- Los Alamos National Lab., NM (United States); and others
The earliest events in protein folding are critically important in determining the folding pathway, but have proved difficult to study by conventional approaches. We have developed new rapid initiation methods and structure-specific probes to interrogate the earliest events of protein folding. Our focus is the pathways. Folding or unfolding reactions are initiated on a fast timescale (10 ns) using a laser induced temperature jump (15 C) and probed with time-resolved infrared spectroscopy. We obtained the kinetics of the helix-coil transition for a model 21-residue peptide. The observed rate constant k{sub obs} = k{sub f} + k{sub u} for reversible kinetics; from the observed rate (6 x 10{sup 6} s{sup -1}) and the equilibrium constant favoring folding of 7.5 at 27 C, we calculate a folding lifetime of 180 ns and an unfolding lifetime of 1.4 {mu}s. The {open_quotes}molten globule{close_quotes} form of apomyoglobin (horse, pH*3, 0.15M NaCl) shows similar kinetics for helix that is unconstrained by tertiary structure (helix with an unusually low Amide I frequency, near 1633 cm{sup -1}). In {open_quotes}native{close_quotes} apomyoglobin (horse, pH*5.3, 10 mM NaCl) two very different rates (45 ns and 70 {mu}s) are observed and we infer that a third occurs on a timescales inaccessible to our experiment (> 1 ms). We suggest that the slower processes are due to helix formation that is rate-limited by the formation of tertiary structure.
- OSTI ID:
- 539068
- Report Number(s):
- CONF-960807-; TRN: 97:004029-0137
- Resource Relation:
- Conference: 212. national meeting of the American Chemical Society (ACS), Orlando, FL (United States), 25-30 Aug 1996; Other Information: PBD: 1996; Related Information: Is Part Of 212th ACS national meeting; PB: 1830 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
The radius of gyration of an apomyoglobin folding intermediate
Ultrafast studies of solution dynamics