Post-translational protein arginylation in plants: localization, dynamics and function
Final Report Abstract
The aim of this project was to investigate post-translational arginylation of plant proteins in the model organism Physcomitrella patens, a moss. This N-terminal modification is an integral part of the N-end rule pathway of protein degradation but is also believed to have protein-stabilizing functions. The study proved to be as challenging as foreseen by all participants and reviewers. Nevertheless, although not all aspects were brought to a conclusion, substantial progress in this field has been achieved. Three independent lossof-function mutants targeting the single gene for arginyl-protein transferase were established. Their examination confirmed identical phenotypes and they are therefore authentic ∆ate lines. Their remarkable and complex growth, cell division, plastid phenotype together with their spectacular starch accumulation is indicative of the central involvement of arginyl-protein transferase activity in the regulation of multiple cellular processes. The use of co-immunopreciptation for the identification of numerous potential interacting partners has demonstrated the utility of this method and established one feasible procedure for addressing the individual components that constitute the signalling pathway from post-translational arginylation to function. The surprisingly low abundance of arginyl protein transferase despite its induction by various environmental factors, proved to be a major hurdle in defining arginylation targets. Despite the detection and identification of several thousand N-termini in cellular extracts by highly sophisticated proteomic approaches, only a single target that passed all tests for false positive/negative criteria was discovered. It transpired to be a member of the N-acylamino acid releasing enzyme family of enzymes that is itself believed to be involved in the process of protein degradation. This revelation emphasizes the potential for arginyl-protein transferase to be involved not merely in the creation of primary destabilizing elements but also in a regulatory capacity. Clearly, extensive further studies are required to comprehend fully the consequences of this discovery.
Publications
- (2011) Simultaneous isolation of pure and intact chloroplasts and mitochondria from moss as basis for sub-cellular proteomics. Plant Cell Reports 30, 205-215
Lang, E.G.E., S.J. Mueller, S.N.W. Hoernstein, J. Porankiewicz-Asplund, M. Vervliet- Scheebaum, R. Reski
