Principal Investigator – Junior Research Group Leader, Institute for Genetics
Dr. Michael Lammers and his team explore the regulation of protein function by post-translational acylation of lysine side chains and how a dysregulation in this post-translational modification contributes to the development of severe diseases such as metabolic syndromes, cancer and neurodegenerative disorders. They have successfully incorporated acetyl-lysine site-specifically into different proteins, amongst others, into small GTP-binding proteins of the Ras superfamily, the tumor suppressor p53 as well as metabolic enzymes and analysed the consequences of lysine-acetylation at the molecular level. Furthermore, they examined the deacetylation reaction catalysed by sirtuin deacetylases and explored determinants of sirtuin substrate specificity. In the future, using this strategy might allow the working group to develop novel therapeutic approaches including the design of deacetylase inhibitors with fewer side effects compared to known compounds.
Our research: Dr. Lammers and his team explore how lysine-acetylation, and further acylations, regulates protein function. Acylation of lysine side chains is one of the most abundant post-translational modifications comparable in number to phosphorylation. It is dynamically regulated by lysine-acyltransferases and lysine-deacylases.
Our successes: Dr. Lammers and his researchers observed that these post-translational modifications regulate protein function using different mechanisms. Therefore, the role of lysine-acylation hast o be analysed on a protein-specific and even on a site-specific basis. Lysine-acetylation can confer a loss-of-function as well as a gain-of-function to proteins. Thereby, these processes can lead to modulations of cellular signal transduction pathways. Sirtuins deacetylate natively-folded substrate proteins with a remarkable specificity, at least for some sites.
Our goals: Dr. Lammers long-term goal is to therapeutically tackle the molecular lysine-acylation machinery. Deacetylase inhibitors have been subject of intensive basic research but they are also in clinical trials in pharmaceutical industry for several years now. However, these compounds often have a low level of target specificity and they show a broad range of unwanted off-target effects. His group focuses on developing more specific therapeutic agents with less side-effects. Mechanistic inhibitors based on non-cleavable acetyl-lysine analogs, such as thioacetyl-lysine, could be used to synthesise highly effective and specific lysine-deacylase inhibitors.
Our methods/techniques: A range of different synthetic biological, biochemical, cell biological and biophysical methods are used in the lab, including isothermal titration calorimetry, stopped flow, microscale thermophoresis and X-ray crystallography.
Figure 1: (A) Lysine-acetylation/acylation is a dynamically regulated post-translational modification catalysed by writers, lysine-acetyltransferases (KATs), and erasers, lysine-deacetylases (KDACs or sirtuins). Acylated lysine side chains can be targeted by readers, bromodomain (BRD) containing proteins. Lysine side chains can be targeted by a variety of different lysine-acylations, including aliphatic, charged and uncharged acylations. For many acylations a rigorous functional characterisation has not been performed so far. (C) We use PylRS, the pyrrolysyl-tRNA-synthetase from Methanosarcina barkeri, as a synthetic-biological tool to incorporate lysine-acylations site-specifically into proteins. (D) The genetic-code expansion concept (GCEC). We use a synthetically evolved acetyl-lysyl-tRNA-synthetase/tRNACUA pair from Methanosarcina bakeri to site-specifically incorporate N-(ε)-acetyl-L-lysine into proteins. In the future, we want to expand our studies also to other lysine acylations.
Figure 2: Structural and functional studies of the effect of lysine-acetylation on protein function. (A) We study the influence of lysine-acylation on the thermodynamics and kinetics of protein-protein interactions and on the protein-structure (B). (C) To disctiminate between biologically important and unimportant sites, we study the impact of lysine-acetylation in mammalian cells/tissues (D) and examine how it is regulated by KDACs, KATs and how it is targeted by BRD-containing proteins.