Research projects in Doreen Dobritzsch group

Pyrimidine metabolism

Nucleotides play an essential role in the cellular energy metabolism and numerous biochemical processes. In most eukaryotes including man, their building blocks uracil and thymine are degraded by the reductive pyrimidine catabolic pathway (Figure 1), which is important for generation of beta-alanine, a GABA-homologue involved in synaptic transmissions, and as main clearance route for the anti-cancer drug 5-fluorouracil (5FU). Deficiencies may cause neurological disorders and death, but controlled inhibition in cancer therapy increases 5FU efficiency, and reduces side effects by allowing lower 5FU dosage. Alternative pathways for pyrimidine degradation exist in a number of prokaryotes and lower eukaryotes. Our aim is to elucidate the structures and mechanisms of pyrimidine-degrading enzymes from different organisms to further our understanding of the diverse catalytic strategies employed for the breakdown of uracil and thymine, to provide frameworks for drug design, and to analyze effects of gene polymorphisms on enzyme activity and 5FU pharmacokinetics.

Highlights: Structural and functional characterization of the three enzymes of the reductive pyrimidine degradation pathway

Current focus: Catalytic core enzymes of a uracil-catabolic pathway used by many yeasts; Regulation of the reductive pathway

Structure image of the reductive pyrimidine-catabolic pathway.

Molecular recognition in RA autoimmune complexes

Rheumatoid arthritis (RA) is a chronic autoimmune disease that affects 0.5-1% of the world’s population. Pathogenesis involves loss of tolerance to the major cartilage protein collagen type II (CII). Further elucidation of RA disease mechanisms is required for development of novel drugs and vaccines that can cure and prevent the disease. We contribute by studying the interactions that occur between self-antigens such as CII and RA-associated immune molecules. This includes autoantibodies with germline or affinity-matured sequence targeting immunodominant CII epitopes in native or post-translationally modified state, to analyze the impact of somatic mutation, epitope conformation and modification on recognition. As susceptibility to RA is strongly associated with polymorphic loci of MHC class II genes, we also determine structures of low and high risk factor MHCII presenting peptides to T cell receptors to reveal the link to RA susceptibility and the role played by posttranslational modifications.

Highlights: Crystal structures of the arthritogenic murine autoantibody Fab fragments CIIC1 (Figure 2) and M2139 in complex with their respective triple-helical CII epitopes

Current focus: Structure elucidation of several other Fab-peptide as well as MHCII-peptide complexes

The structures of the arthritogenic murine autoantibody Fab fragments.

Additional projects

In collaboration with other research groups we aim at structural and functional characterization of a number of different enzymes/proteins and their ligand complexes that will further our knowledge about fundamental life processes, support industrial application of these proteins in biocatalytic transformations, or facilitate the design of strong binding inhibitors that may be developed into novel drugs.