Günther Jung built up one of the most recognized European research groups working in peptide and natural product chemistry and in immunochemistry. His research activities comprised challenging design with perfectly applied innovative synthetic and analytical methods. The results of his interdisciplinary and competitive research have a long-lasting impact in various fields of molecular immunology, microbiology and even biophysics. Thus, his research initiated progressing success by younger leading scientists.
How ions travers lipid membranes without carriers
The structure elucidation and synthesis of polypeptide antibiotics which induce voltage-dependent ion conducting ion channels in lipid bilayer membranes was one of his earlier research topics. The first detailed biophysical investigations on natural and synthetic peptaibols allowed to propose a model for the gating mechanism. Novel synthetic, template-free polypeptide aggregates exhibit single channel fluctuations similar to those of the acetylcholine receptor.
From a linear peptide hormone to cyclic, size reduced leads
The first extensive structure-activity relationships of neuropeptide Y were published by his laboratory. The 36-peptide amide was reduced to a small cyclic lead structure which served for the design of NPY antagonists with potential applications as therapeutics. Advanced methods of multiple peptide synthesis in combination with HPLC-ESI-MS/MS enabled his laboratory to produce exceptionally good characterized large sets of peptides in various fields.
Genetic engineering of antibiotics with sulfide rings and heterocycles, a break-through in antibiotic biosynthesis
In collaboration with microbiologists Günther Jung’s group elucidated the structure of an impressive number of secondary microbial metabolites, in particular peptide antibiotics with unusual residues and peptide siderophores. Since 1986 he worked on the lantibiotics. These polycyclic bacteriocins contain lanthionines and α,β-didehydroamino acids and have molecular masses up to 3500. The elucidation of about 15 new lantibiotics and the solution structures of gallidermin, actagardine, duramycins and Pep5 by 2D-NMR have been performed.
One of the highlights was the first experimental proof of the biosynthetic principle of the lantibiotics in cooperation with microbiologists (published in Nature 1988). Other than common peptide antibiotics, lantibiotics including nisin are synthesized via enzymatic modification of prepeptides based on structural genes. Novel possibilities of peptide bioengineering allowed the production of new polypeptides containing unsaturated amino acids and sulfide rings.
Key intermediates of lantibiotic biosynthesis could be elucidated consisting of a leader peptide followed by a propeptide with up to six dehydrated Ser, Thr residues without the sulfide bridges. The isolation of the novel enzymes involved in the modification of the prelantibiotics was fast progressing and their substrate specificity was studied successfully using combinatorial libraries. For example, the specificity of new flavoenzymes which catalyze C-terminal oxidative decarboxylations of peptidyl-cysteines have been characterized by library approaches with HPLC-FTICR-MS and NMR.
A further highlight was the determination of the structure of the 43-peptide antibiotic microcin B17, a gyrase inhibitor containing 8 thiazole and oxazole backbone modifications. This impressive elucidation was done by MS and 2D-NMR on 13C, 15N-labelled microcin. In 1996 the first synthesis of this most prominent polypeptide and analogues was published. Many more complex peptide antibiotics have been elucidated by G. Jung’s group such as omphalotin and biosynthetic linear key precursors of vancomycin type antibiotics with a great potential for combinatorial biosynthesis.
How to characterize protein binding sites using fast and exact mapping
Günther Jung’s group carried out the complete epitope mapping of countless proteins to develop diagnostic tools or vaccines. The fine mapping of T-helper, CTL- and B-cell epitopes of HIV protein Nef, tissue plasminogen activator t-PA, and thymidine kinase of Herpes simplex are noteworthy as well as the complete HCV genome coded protein. He combined methods for conformational mapping using circular dichroism, epitope determination and prediction for the experimentally supported molecular modelling of structurally unknown proteins. The 55-peptide NCP7 of HIV-1 with two Zn-finger regions was synthesized in excellent purity and studied for its biological role.
Minimal lipopeptide vaccines showed virus-specific killer cell responses in vivo. A breakthrough in molecular immunology and synthetic vaccines
Fundamental advances in the current understanding of T-cell responses originated from his immunological peptide research. The pioneering development of synthetic low-molecular weight lipopeptide vaccines was based on his idea to use the natural N-terminus of E.coli lipoprotein as built-in adjuvant/carrier principle for antigenic determinants as early as 1985. This tripalmitoyl-S-glyceryl-cysteine residue coupled to T-cell and B-cell epitopes, constitutes a novel type of synthetic vaccine with no need for additional protein carrier or adjuvants. Structure-activity relationships of such lipopeptides acting as agonists on Toll-like receptors TLR 1/2 and TLR 2/6 have been determined and also a TLR 2 inhibitor was developed in his laboratory. A lipopeptide vaccine of only 3500 daltons was protective against foot-and-mouth disease virus in cattle and showed high titers of virus neutralizing antibodies.
Using his lipopeptide approach the in vivoinduction (priming) of virus specific cytotoxic T-lymphocytes (CTL or killer cells) was realized for the first time (publ. in Nature 1989). This fundamental work had a high impact and demonstrated a way to introduce peptides in vivo in the processing pathway of MHC-I and II antigen presenting cells. The lipopeptide vaccines are in clinical trials and in veterinary applications. The lipopeptides for research are now commercially available.
K.H. Wiesmüller (CEO of EMC microcollections GmbH) developed the lipopeptide Pam3Cys-XS15 adjuvant. In clinical trials multipeptide vaccines with the novel adjuvant showed long lasting specific B-and strong T-cell responses against glioblastoma tumors and COVID-19 (J.S. Heitmann et al., Nature online, Nov. 23, 2021).
Sequencing of natural peptides responsible for individual cellular immune reponses, a fundamental progress in molecular immunology and therapy
Together with cell biologists his group developed a direct method for the extraction and pool sequencing of naturally processed MHC (HLA) bound peptide ligands, so called self-peptides (publ. in Nature 1990, 1991, 1993). For the first time one of his PhD students determined experimentally that MHC molecules present natural octa- or nonapeptide libraries on the cell surface, which exhibit defined sequence motifs of conserved anchor residues characteristic for each MHC-allele. This finding is of fundamental importance for the development of immunotherapeutic drugs based on MHC/T-cell interactions. Current clinical applications and start-up companies are based on these research results.
Single agonists and antagonists from synthetic mixtures with millions of peptides
Exciting results were found using highly complex synthetic peptide libraries for the ultimate definition of the ‘’immunological code’’ based on exact peptide ligand motifs for MHC I and II. This is an experimental proof of the motifs of natural libraries with synthetic libraries. Moreover, the fine specificities and degeneracy of T-cells isolated from patients with autoimmune disease could be determined via peptide libraries. Highlights were the first definition of 10 000 to 100 000 times more active superagonists for human T-cell clones and of a variety of peptidomimetic T-cell antagonists. In cooperations the natural processing and transport of antigenic fragments via proteasomes and TAP transporters using synthetic libraries and peptidomimetics has been studied.
The practical challenges of combinatorial organic chemistry
Günther Jung is one of the earlier pioneers of automatedcombinatorial organicchemistry in Germany, developing methods for parallel synthesis and accurate instrumental analysis of compound libraries. This work includes protocols for single compound libraries of innumerable heterocyclic scaffolds, one-bead-one-compound libraries and analytical methods from IR-microscopy of polymer beads to nano-HPLC-FTICR-MS on monolithic columns. The single bead, enantiomer and cyclopeptide library analyses were established. His research also included parallel solution phase chemistry and the development of polymer bound reagents. His first publication in this field can be found in Angew. Chem. as early as in 1977 (!). Pioneering and collaborative work has been carried out in the fields of novel biosensors and chemosensors which includes cyclopeptide functionalized surfaces and newly designed matrix supported bilayers for membrane bound proteins and cellular assays.
Biotech foundations based on academic research
G. Jung is cofound together with his doctorands of two companies in Tübingen. EMC microcollections GmbH (1996) is producing organic compound collections, lipopeptide vaccines, peptides and peptidomimetics for lead finding and optimization. CureVac AG (1999) is producing mRNA vaccines according to GMP protocols tested in clinical antitumour therapy and immunization against infectious diseases. The wellknown DNA/RNA transfection reagent (Effectene, a cationic lipid) has been developed in his laboratory which is very successful on the market.