Dr. Carl Frieden

Professor
Department of Biochemistry and Molecular Biophysics

Biochemistry Program
Molecular Biophysics Program
Molecular Cell Biology Program

Current Lab Members and Collaborators:

Dr. Carl Frieden, Dr. Jenny Buzan, Dr. Clay Clark, Dr. Tim Close, Dr. George Drysdale, Jinyan (Lee) Du, Dr. Sydney Hoeltzli, Dr. Brad Karon, Dr. Keehyuk Kim, Ran Kim, and Dr. Linda Kurz

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KINSIM and FITSIM Downloads

You can download the newest versions of Kinsim and Fitsim for the PC from this site. Click Here to view the release notes and download the compressed file. You will also find a link to a short help page. Another PC program, KSIM, is also described on this page.

Overview of Research Projects

groel dhfr ifabp actin
GroEL DHFR IFABP Actin


Protein folding, protein structure/function relationships, protein-protein interactions and the mechanism of enzymatic reactions are projects currently under study in this laboratory.

The long term goal of the protein folding studies is to understand the nature of the intermediate structures on the unfolding and refolding pathways, including the role of proteins that assist folding (called chaperonins). The work uses site-directed mutagenesis and techniques such as 19F and proton NMR, circular dichroism, fluorescence measurements and x-ray crystallography. Proteins in these studies include the intestinal fatty acid binding protein, dihydrofolate reductase, actin, and GroEL.

Studies on protein-protein interactions are related to the folding studies but also include actin, actin binding proteins and polymerization processes. The long term goal of this work is to understand the role of actin in maintaining the cytoskeletal structure of cells and how such structures control cellular functions. Studies on site-directed mutants of actin are underway.

The long term goal of kinetic studies with enzymes is to understand the catalytic mechanism of specific enzymatic reactions.

For a List of References on These and Other Projects Click Here

Specific Research Projects


groel


Interactions of the Molecular Chaperonin GroEL with Dihydrofolate Reductase



The goal of this work is to understand the GroEL-mediated folding mechanism. GroEL is a member of the Hsp60 class of chaperones, which are tetradecamers of identical 57.2 kDa monomers. The chaperonin binds unfolded proteins and generally increases the final yield of native protein without increasing the rate of folding. The formation of stable complexes with GroEL is most often discussed, and while, for example, murine dihydrofolate reductase (MuDHFR) does form a stable complex, the complex formed with the structurally homologous E. coli DHFR (EcDHFR) is transient (at 22 degrees C). For both DHFRs, the concentration of bound protein increases as the temperature is increased. Using a variety of biophysical approaches, we are examining the kinetic mechanism of folding as well as the thermodynamic parameters for the binding of these DHFRs with GroEL.
To read recent abstracts of this work click Here.


dhfr


Real-time Folding Studies of E. coli DHFR using 19F Stopped-flow NMR



In this work, we are studying sidechain environment and behavior during the refolding of E. coli dihydrofolate reductase (DHFR) in real time by stopped-flow NMR techniques. E. coli dihydrofolate reductase has five tryptophans which have been replaced with 6-19F-tryptophan. The resonances assigned to each tryptophan are resolved in both unfolded and native DHFR, allowing us to monitor the environment of individual tryptophans during unfolding and refolding in real time using stopped-flow 19F NMR techniques. The refolding and unfolding kinetics have also been examined by stopped-flow circular dichroism and stopped-flow fluorescence techniques and compared to the changes in sidechain environment observed by stopped-flow 19F NMR.
To read recent abstracts of this work click Here.


ifabp


Folding Studies of Intestinal Fatty Acid Binding Protein



The goal of this project is to determine the mechanism of folding of the intestinal fatty acid binding protein (IFABP). This protein is one of a family of proteins that bind fatty acids, bile salts and retinoids. This family is primarily beta-sheet with a large central cavity into which the ligand binds. Cysteine- and proline-free, IFABP is a model protein for studying the mechanism of folding. Current research concerns the role of turns in the folding process.
To read recent abstracts of this work click Here.


actin


Folding and Polymerization of Actin



The goal of this work is to understand the molecular mechanism of actin polymerization and filament function. We are investigating the role of specific amino acid residues in the mechanism by comparing the kinetics of self- polymerization of mutant actin proteins with that of wild type, in the presence and absence of various actin binding proteins. Because yeast genes are more readily manipulated than those of higher eucaryotes, we are primarily studying yeast actin including the Wertman alanine substitution mutants (Wertman, K.F., Drubin, D.G. & Botstein, D. (1992) Genetics 132, 337-350) and several actin mutations that have been phenotypically characterized in nematodes (Robert Waterston, Washington University School of Medicine), which we have put into yeast actin . We have monitored the reactions via the fluorescence change of trace pyrene-actin as it is incorporated into filaments, or via the change in the intrinsic fluorescence of unlabeled actin upon filament formation.
To read recent abstracts of this work click Here.


Dr. Carl Frieden <frieden@biochem.wustl.edu>
Department of Biochemistry and Molecular Biophysics, Box 8231
Washington University School of Medicine
660 South Euclid
St. Louis, MO 63110 (USA)
office: 314-362-3344
lab: 314-362-3342
or -3359
FAX: 314-362-7183
send mail to frieden@biochem.wustl.edu

URL: http://biochem.wustl.edu/cflab
last update: $Date: 10/13/97$
This site is maintained by Clay Clark
Send comments to: clark@biochem.wustl.edu