Book of Abstracts: Albany 2009
June 16-20 2009
© Adenine Press (2008)
Molecular Anatomy Of The Human Pathogen Leptospira interrogans
Systems biology conceptualizes biological systems as dynamic networks of interacting molecules, whereby functionally important properties are thought to emerge from the structure of such networks. Due to the ubiquitous role of complexes of interacting proteins in biological systems, their subunit composition and temporal and spatial arrangement within the cell are of particular interest. While cellular proteomics provides an average picture of the protein expression for all the cells used in a particular study, visual proteomics resembles a bridge to the observation of individual macromolecules within the context of single cells. Although, the structural signature of large protein complexes can in principle be recognized within cryo electron tomograms of intact cells, this concept has so far only been applied unambiguously for ribosomes. A major difficulty is the proteome wide determination of the cellular protein concentration and its variability from cell to cell.
We have tackled this problem for the human pathogen Leptospira interrogans by a combined strategy of cryo electron tomography and quantitative mass spectrometry. We used cryo-electron tomography and template matching to observe several protein complexes involved in bacterial stress response in the cytoplasm of intact cells. Target-driven mass spectrometry, in particular inclusion list based LTQ-FT experiments and multi reaction monitoring served for relative and absolute quantification of the same protein complexes and further proteins involved in the same biological processes. To localize protein complexes within the cytoplasm, we employed statistical concepts used for peptide matching in proteomics to template matching within tomograms of intact L. interrogans cells. We investigated stress response in a heat-shocked (fever), antibiotics-treatment and starved condition by targeted and visual proteomics.
Institute of Molecular Systems Biology