One of the major unsolved problems of molecular biophysics involves determining how proteins fold. Steady-state fluorescence changes of intrinsic tryptophan fluorescence have been utilized to monitor folding transitions in proteins for many years. From these studies, only kinetic arguments concerning the mechanism of folding transitions could be made. In this proposal, a new class of fluorescence experiments are introduced: stooped-flow time- resolved fluorescence. In these studies, a high repetition picosecond laser is utilized for excitation, and the fluorescence emission is detected by sixteen independent time-resolved single photon counting channels. In this manner, complete time-resolved fluorescence decay can be obtained in as little as 10 milliseconds. The addition information content of the time-resolved experiments allows stopped-flow studies to examine not just the kinetics of a transition but also the mechanism. Studies are performed on the single tryptophan containing Staphylococcal Nuclease and site- specific mutants. Changes in the intrinsic tryptophan fluorescence in this protein was first used by Anfinsen's group in 1971 to unequivocally demonstrate the existence of kinetic intermediates in the refolding of proteins. However, no insight into the physical nature of the intermediate form(s) of this protein have ever been obtained. From examination of the millisecond changes in lifetimes and rotational correlation times of nuclease during refolding, the time-course of localized and native-like structure formation are observed, as well as the solvent exposure history of the single tryptophan residue. A series of site-specific mutants have been constructed, specifically designed for performing energy transfer experiments between the single tryptophan and acceptor groups located throughout the structure of nuclease. From examination of these mutants millisecond motion pictures of the refolding transition are obtained. Although Staphylococcal Nuclease and its site-specific mutants are targeted for investigation, the methodologies developed in this proposal will be beneficial for all studies which utilize the kinetics of changes in steady-state fluorescence to monitor biological transitions (e.g., ligand binding, protein association reactions, protein:DNA interactions, etc.).

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM045990-01
Application #
3305488
Study Section
Molecular and Cellular Biophysics Study Section (BBCA)
Project Start
1991-05-01
Project End
1994-04-30
Budget Start
1991-05-01
Budget End
1992-04-30
Support Year
1
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
Whitesell, Richard R; Ardehali, Hossein; Beechem, Joseph M et al. (2005) Compartmentalization of transport and phosphorylation of glucose in a hepatoma cell line. Biochem J 386:245-53
Allan, B W; Reich, N O; Beechem, J M (1999) Measurement of the absolute temporal coupling between DNA binding and base flipping. Biochemistry 38:5308-14
Bilsel, O; Yang, L; Zitzewitz, J A et al. (1999) Time-resolved fluorescence anisotropy study of the refolding reaction of the alpha-subunit of tryptophan synthase reveals nonmonotonic behavior of the rotational correlation time. Biochemistry 38:4177-87
Beechem, J M; Otto, M R; Bloom, L B et al. (1998) Exonuclease-polymerase active site partitioning of primer-template DNA strands and equilibrium Mg2+ binding properties of bacteriophage T4 DNA polymerase. Biochemistry 37:10144-55
Meagher, J L; Beechem, J M; Olson, S T et al. (1998) Deconvolution of the fluorescence emission spectrum of human antithrombin and identification of the tryptophan residues that are responsive to heparin binding. J Biol Chem 273:23283-9
Otto, M R; Bloom, L B; Goodman, M F et al. (1998) Stopped-flow fluorescence study of precatalytic primer strand base-unstacking transitions in the exonuclease cleft of bacteriophage T4 DNA polymerase. Biochemistry 37:10156-63
Lanzo, C A; Beechem, J M; Talley, J et al. (1998) Investigation of the binding of isoform-selective inhibitors to prostaglandin endoperoxide synthases using fluorescence spectroscopy. Biochemistry 37:217-26
Beechem, J M (1997) Picosecond fluorescence decay curves collected on millisecond time scale: direct measurement of hydrodynamic radii, local/global mobility, and intramolecular distances during protein-folding reactions. Methods Enzymol 278:24-49
Lillo, M P; Beechem, J M; Szpikowska, B K et al. (1997) Design and characterization of a multisite fluorescence energy-transfer system for protein folding studies: a steady-state and time-resolved study of yeast phosphoglycerate kinase. Biochemistry 36:11261-72
Lillo, M P; Szpikowska, B K; Mas, M T et al. (1997) Real-time measurement of multiple intramolecular distances during protein folding reactions: a multisite stopped-flow fluorescence energy-transfer study of yeast phosphoglycerate kinase. Biochemistry 36:11273-81

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