Protein kinase B (PknB) of Mycobacterium tuberculosis is essential for growth of the pathogen in vitro as well as for survival within the host.
The Mycobacterium tuberculosis protein kinase B (PknB) comprises an intracellular kinase domain, connected through a transmembrane domain to an extracellular region that contains four PASTA domains. The present study describes the comprehensive analysis of different domains of PknB in the context of viability in avirulent and virulent mycobacteria. We find stringent regulation of PknB expression necessary for cell survival, with depletion or overexpression of PknB leading to cell death. Although PknB-mediated kinase activity is essential for cell survival, active kinase lacking the transmembrane or extracellular domain fails to complement conditional mutants not expressing PknB. By creating chimeric kinases, we find that the intracellular kinase domain has unique functions in the virulent strain, which cannot be substituted by other kinases. Interestingly, we find that although the presence of the C-terminal PASTA domain is dispensable in the avirulent M. smegmatis, all four PASTA domains are essential in M. tuberculosis. The differential behavior of PknB vis-à-vis the number of essential PASTA domains and the specificity of kinase domain functions suggest that PknB-mediated growth and signaling events differ in virulent compared with avirulent mycobacteria. Mouse infection studies performed to determine the role of PknB in mediating pathogen survival in the host demonstrate that PknB is not only critical for growth of the pathogen in vitro but is also essential for the survival of the pathogen in the host.
From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and.
Yogesh
Y
Chawla
From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and.
Sandeep
S
Upadhyay
From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and.
Shazia
S
Khan
From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and.
Sathya Narayanan
SN
Nagarajan
the Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
Francesca
F
Forti
From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110067, India and Vinaykn@nii.ac.in.
Vinay Kumar
VK
Nandicoori
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D005110:Extracellular Space / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D042541:Intracellular Space / Q000378:metabolism; D051379:Mice; D050296:Microbial Viability; D009169:Mycobacterium tuberculosis / Q000166:cytology* / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport
C475060:PknB protein, Mycobacterium tuberculosis; D017346:Protein Serine-Threonine Kinases
Bacterial Protein Kinases; Cell Growth; Cell Signaling; Mycobacteria; PASTA Domain; PknB; Protein Phosphorylation