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Max-Planck-Forschungsstelle für Enzymologie der Proteinfaltung

Profile of the Institute The “ Enzymology of Protein Folding” research centre of the Max Planck Society was founded in June 1996 under direction of Gunter S. Fischer. Since September 1998 the research centre is accomodated in the newly built complex of the BIOCENTER Halle. Members of the research centre represent the topics Protein Chemistry, NMR-Spectroscopy and spectroscopic methods in Biochemistry in lectures, seminars and practical courses at the course of study at the insitut of Biochemistry / Biotechnology of the Martin-Luther-University Halle-Wittenberg.

Work of the Institute

Originating from the non-permanent research group "Enzymology of the Peptide Bond" of the Max Planck Society, the research division "Enzymology of Protein Folding" was founded in 1997. Research focuses on the principles of conformational changes controlling the biological activity of peptides and proteins.

The ability of a polypeptide to fold into a three-dimensional state of unique biological function is still an enigma. Many diseases are caused by misfolding, improper restructuring of protein segments and non-natural chain stability. Pathological changes in tissues may also arise from aberrant folding helper proteins, as chaperones and folding helper enzymes.

Mainly rotational movements about covalent bonds determine the course of protein folding. Intrinsically slow in its dynamics, the cis/trans isomerization of peptide bonds is partially uncoupled from other conformational interconversions of a protein backbone, thus providing a useful probe for investigations on the molecular level in vitro and in vivo. Almost complete uncoupling occurs when the gene-coded amino acid proline makes up part of the peptide bond at the nitrogen side. Under these conditions the chain movement resembles an on/off switch regulating atomic distances in the protein backbone.

By its chemical nature, proline is a unique member of the gene-coded amino acids. Molecular approaches to chemical and biological differences of peptide bond isomers of proline-containing polypeptides are currently being explored. Work includes evaluation of the slow interconversion dynamics of biologically relevant peptides and proteins such as angiotensin II, HIV-1 capsid protein fragments, phosphorylated proteins and others, which function either as ligands or receptors in their respective biological context. In addition to conventional biochemical techniques, other methods utilized include dynamic nuclear magnetic resonance spectroscopy and laser-induced photochemical reactions at substituted peptide bonds. Chemical syntheses of proline-surrogates, peptide bond mimetics and oligopeptide libraries are performed in the peptide synthesis laboratory.

Considerable research activity focuses on the characterization of enzymes possessing proline- specificity. Such enzymes include folding helper enzymes, like peptidyl prolyl cis/trans isomerases, proline-specific protein kinases and protein phosphatases and proline-specific proteases. They are mostly involved in events critical for cell signalling, host/pathogen interaction and development. Consequently, sensitive assays have been developed which are able to operate under conditions typical of high throughput screening technologies. These methods serve to pick out from chemical compound libraries lead structures for drug development. In the assays, the targeted proteins are isolated from authentic sources, as recombinant wild type proteins and as protein variants covering site-directed mutation.

The unique nature of proline in the context of a polypeptid chain can often lead to molecular mechanisms for proline-limited protein folding, proline-specific protein/ligand associations and proline-specific enzyme/substrate interactions distinct from events lacking proline involvement. The principles governing the relationship between proline-specific properties and the biological function of proteins are being investigated. Specific inhibitors of proline-specific enzymes provide a powerful tool for exploring their role in cell functions. The immunosuppressant drugs cyclosporin A, rapamycin and FK506 represent tight binding inhibitors of peptidyl prolyl cis/trans isomerases, for example. A new lead structure selective for the inhibition of a family of the peptidyl prolyl cis/trans isomerases has been developed which demonstrates considerable activity in an animal neuroregeneration model.

The Junior Research Group was established in 1999. Using mitochondria from yeast as a model system, research chiefly focuses on understanding the role and function of chaperones in vivo. The majority of proteins which are localized in the mitochondria are synthesized in the cytosol and subsequently imported into the organelle. Mitochondria are essential for eucaryotic life and contain a number of essential proteins, all of which are involved in protein import. The import process has been studied in detail: the energetic requirements have been defined, and most of the components of the import machinery in the outer and inner membrane have been identified. Much less is known about cytosolic proteins involved in mitochondrial import. These proteins are thought to have chaperone-like properties and maintainthe mitochondrial precursor proteins in an import competent state. The aim of research is to define the role of cytosolic factors during the early steps of mitochondrial protein import.

While precursor proteins cross the mitochondrial membranes they have to be in an unfolded conformation, and subsequently they have to refold in the matrix. For this reason, the import of in vitro synthesized mitochondrial proteins into isolated mitochondria is an excellent system for studying protein folding under conditions that mimic those existing in vivo. The folding process in vivo is assisted by chaperone proteins. Their function, specificity, and mechanism of action has been the focus of research over the past few years. One key goal is to obtain an understanding of protein folding in a living cell.



Max-Planck-Forschungsstelle für Enzymologie der Proteinfaltung

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