The network of protein quality control factors in the cell envelope of Escherichia coli
Final Report Abstract
Protein quality control involves sensing and treatment of defective or fragmented protein structures. Misfolded or mislocalized proteins trigger dedicated signal transduction cascades that upregulate the production of protein quality control factors. Corresponding folding catalysts, chaperones and proteases either repair or degrade damaged proteins thereby reducing the level of aggregation-prone molecules. Since the periplasm of Gram-negative bacteria is particularly exposed to environmental changes and respective protein folding stresses that are connected with the presence of detergents, low or high osmolarity of the medium, elevated temperatures and the host's immune response, fine-tuned protein quality control systems are essential for survival under these unfavourable conditions. 137 candidate substrates of folding factors and proteases in the E. coli cell envelope have been identified. These proteins belong to 4 major classes, i.e. outer membrane proteins, lipoproteins, enzymes of cell wall homeostasis, and binding proteins of ABC transporters. This large set of candidates is expected to be useful for future studies addressing mechanistic aspects of proteostasis. During the initial characterisation of these candidates, the glucose-1-phosphate phosphatase Agp appeared to be suitable to serve as a model substrate for in vitro and in vivo analyses of protein folding and degradation questions. Moreover, a software package, UMSAP, has been developed allowing convenient processing of mass spectrometry data. These data are instrumental to obtain an increased temporal and spatial understanding of proteolytic processes. Another example of the usefulness of mass spectrometry is a study in which the extent of occupancy of allosteric ligands could be correlated to the dynamic and general mechanism of activation by oligomerisation. In addition, initial evidence was obtained for the formation of structured protein aggregates in the cell envelope suggesting the potential for a new field of research.
Publications
- 2013. The diversity of allosteric regulation in proteases. ACS Chem Biol 8:19-26
Merdanovic, M, Mönig, T, Ehrmann, M and M Kaiser
(See online at https://doi.org/10.1021/cb3005935) - 2014. Substrate Occupancy at the Onset of Oligomeric Transitions of DegP. Structure 22: 281–290
Thompson, NJ, Merdanovic, M, Ehrmann, M, van Duijn, E, and Heck, AJR
(See online at https://doi.org/10.1016/j.str.2013.11.010) - Mass Spectrometry Utilities: Fast analysis of mass spectrometry data. 2018. Rapid Commun. Mass Spectrom. 32:1659-1667
Bravo-Rodriguez, K, Hagemeier, B, Drescher, L, Lorenz, M, Meltzer, M, Kaschani, F, Kaiser, M and M Ehrmann
(See online at https://doi.org/10.1002/rcm.8243)
