Towards the Characterization of Putative Degradation Targets of Klebsiella pneumoniae Lon Protease by Quantitative Proteomics and in vitro Degradation Assays

Abstract

Klebsiella pneumoniae is an opportunistic bacterial pathogen, possessing numerous virulence factors to adapt to harsh host environments. Lon is an ATP-dependent serine protease in K. pneumoniae and was recently discovered to have a potential role in iron homeostasis. To identify potential targets of Lon impacting iron-homeostasis, this study used quantitative proteomics to identify proteins with significantly increased or decreased abundance binding to Nickel-Nitriloacetic acid agarose in the presence or absence of hexahistidine-tagged Lon. Candidate target proteins were purified and tested against Lon in vitro for degradation. Our results identified further links between Lon and iron-related proteins, while also uncovering a strong connection between Lon and sulfur metabolism/amino acid synthesis proteins in the Cys family. Overall, this work begins to test the potential interactions between Lon and proteins involved in iron homeostasis and uncovers a potential new role for Lon in sulfur homeostasis.