Ability of PknA, a mycobacterial eukaryotic-type serine/threonine kinase, to transphosphorylate MurD, a ligase involved in the process of peptidoglycan biosynthesis

Institute of Microbial Technology, Council of Scientific and Industrial Research, Sector 39A, Chandigarh 160 036, India.
Biochemical Journal (Impact Factor: 4.4). 07/2008; 415(1):27-33. DOI: 10.1042/BJ20080234
Source: PubMed


Eukaryotic-type serine/threonine protein kinases in bacteria have been implicated in controlling a host of cellular activities. PknA is one of eleven such protein kinases from Mycobacterium tuberculosis which regulates morphological changes associated with cell division. In the present study we provide the evidence for the ability of PknA to transphosphorylate mMurD (mycobacterial UDP-N-acetylmuramoyl-L-alanine:D-glutamate-ligase), the enzyme involved in peptidoglycan biosynthesis. Its co-expression in Escherichia coli along with PknA resulted in phosphorylation of mMurD. Consistent with these observations, results of the solid-phase binding assays revealed a high-affinity in vitro binding between the two proteins. Furthermore, overexpression of m-murD in Mycobacterium smegmatis yielded a phosphorylated protein. The results of the present study therefore point towards the possibility of mMurD being a substrate of PknA.

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    • "It has been suggested that the MurD reaction is the step at which PG synthesis is regulated to maintain the relative thickness of the PG layer in Gram-negative bacteria (Walsh et al., 1999). Furthermore , Mycobacterium tuberculosis MurD is a substrate of PknA kinase, and transphosphorylation of MurD might be involved in the regulation of a switch between PG biosynthesis and cell division in mycobacteria (Thakur and Chakraborti, 2008). "
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    • "The role of PknA in regulating cell division in mycobacteria was also confirmed in another study showing modulation of FstZ activity by PknA [66]. Furthermore, also cell wall synthetic enzymes such as MurD, GlmU, and PbpA appear to be regulated by PknA or PknB, supporting the strong relation existing between STPK-dependent phosphorylation and peptidoglycan biosynthesis in cell elongation [67-69]. "
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    ABSTRACT: Recent genetic, biochemical and structural studies have established that eukaryotic-like Ser/Thr protein-kinases are critical mediators of developmental changes and host pathogen interactions in bacteria. Although with lower abundance compared to their homologues from eukaryotes, Ser/Thr protein-kinases are widespread in gram-positive bacteria. These data underline a key role of reversible Ser/Thr phosphorylation in bacterial physiology and virulence. Numerous studies have revealed how phosphorylation/dephosphorylation of Ser/Thr protein-kinases governs cell division and cell wall biosynthesis and that Ser/Thr protein kinases are responsible for distinct phenotypes, dependent on different environmental signals. In this review we discuss the current understandings of Ser/Thr protein-kinases functional processes based on structural data.
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    • "In most bacterial proteomes, however, it is difficult to predict which proteins are phosphorylated and which processes are in fact regulated by phosphorylation of Ser/Thr/Tyr. It is also not clear which kinases are involved in the phosphorylation of respective proteins, although a few protein kinases that were found to phosphorylate specific proteins have been identified [16] [17] [18] [19] [20] [21]. Development of phosphoproteomics has enabled us to determine phosphorylation sites of proteins precisely. "
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