Access Type

Open Access Dissertation

Date of Award

January 2014

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biological Sciences

First Advisor

Choong-Min Kang

Abstract

To respond to environmental changes, M. tuberculosis possesses eleven "eukaryotic-type" Ser/Thr protein kinases. The aim of the study described in this dissertation was to identify role of two of these kinases; PknA and PknB that are essential in M. tuberculosis. Two approaches are described to screen for potential in vivo substrates of PknA/PknB. First approach is based on proteomic search by over-expressing PknA/PknB in M. tuberculosis. Proteomic search led to identification of proteasome to be a substrate of PknA and PknB in M. tuberculosis. Furthermore, I demonstrate that the phosphorylation of PrcA and PrcB by PknA regulates processing of Pre-PrcB. Additionally, I show that PknA phosphorylation of pre-PrcB and PrcA reduces the assembly of the proteasome complex and thereby enhances mycobacterial resistance to H2O2. Thus, H2O2 stress diminishes the formation of the proteasome complex in a PknA-dependent manner. The second approach to identify potential in vivo substrates is by a homology search using the preferred phosphorylation motif ATQXIP identified based on already known in vivo substrates of PknA/PknB. This screen identified 7 new putative substrates of PknA/PknB and I chose to investigate the candidate substrate FbpB.

This study has confirmed the role of PknA and PknB in regulating holo-proteasome assembly, function, and aso highlighted the possible role of M. tuberculosis proteasome in oxidatice stress response. The phosphorylation of proteasome is important for increasing resistance to H2O2 has been reported for the first time in this study. This study was also the first time that identified secreted form of FbpB has reduced mycolyl transferase activity when compared to intracellular FbpB and that the residue 234T is important for FbpB enzyme activity possibly due to their different phosphorylation status.

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