Role ofMycobacterium tuberculosisSer/Thr Kinase PknF: Implications in Glucose Transport and Cell Division

Abstract

Protein kinases have a diverse array of functions in bacterial physiology, with a distinct role in the regulation of development, stress responses, and pathogenicity. pknF, one of the 11 kinases of Mycobacterium tuberculosis, encodes an autophosphorylating, transmembrane serine/threonine protein kinase, which is absent in the fast-growing, nonpathogenic Mycobacterium smegmatis. Herein, we investigate the physiological role of PknF using an antisense strategy with M. tuberculosis and expressing PknF and its kinase mutant (K41M) in M. smegmatis. Expression of PknF in M. smegmatis led to reduction in the growth rate and shortening and swelling of cells with constrictions. Interestingly, an antisense strain of M. tuberculosis expressing a low level of PknF displayed fast growth and a deformed cell morphology compared to the wild-type strain. Electron microscopy showed that most of the cells of the antisense strain were of a smaller size with an aberrant septum. Furthermore, nutrient transport analysis of these strains was conducted using 3 H-labeled and 14 C-labeled substrates. A significant increase in the uptake of D-glucose but not of glycerol, leucine, or oleic acid was observed in the antisense strain compared to the wild-type strain. The results suggest that PknF plays a direct/indirect role in the regulation of glucose transport, cell growth, and septum formation in M. tuberculosis.

TheMycobacterium tuberculosisGroEL1 Chaperone Is a Substrate of Ser/Thr Protein Kinases

“…M. tuberculosis PknF participates in multiple biological processes, such as cell growth, septum formation, and glucose transport (8). It has been shown to phosphorylate the two Forkhead-associated domains of the ABC transporter protein Rv1747 (7,26) and the Forkhead-associated domain of Rv0020 (13 with previous reports on other mycobacterial kinases (24).…”

Bacterial Growth and Cell Division: a Mycobacterial Perspective

“…PknF has been shown to phosphorylate M. tuberculosis Rv1747, a predicted ABC transporter (83,169,287). When PknF, which is absent in M. smegmatis, is overexpressed in M. smegmatis, the bacteria grow slowly and are short and swollen (103). Furthermore, when PknF is depleted from M. tuberculosis, the cells grow more rapidly, are small, have aberrant septum formation, and have a 16-fold increase in glucose uptake (103).…”

“…When PknF, which is absent in M. smegmatis, is overexpressed in M. smegmatis, the bacteria grow slowly and are short and swollen (103). Furthermore, when PknF is depleted from M. tuberculosis, the cells grow more rapidly, are small, have aberrant septum formation, and have a 16-fold increase in glucose uptake (103). Phosphorylation of ABC transporters is known to affect activity and stability (97,190), and thus PknF may regulate glucose uptake through phosphorylation of Rv1747.…”

The Mycobacterium tuberculosis β-Ketoacyl-Acyl Carrier Protein Synthase III Activity Is Inhibited by Phosphorylation on a Single Threonine Residue

“…The M. tuberculosis genome contains 11 Ser/Thr protein kinases (STPKs) 6 (4,5), and most are being investigated for their physiological roles and potential application for future drug development to combat tuberculosis (6). This significant number of STPKs suggests that phosphorylation may influence a wide range of biological functions, such as adaptation to various environmental conditions, stress, cell wall synthesis, cell division, and pathogenicity (7)(8)(9)(10)(11)(12)(13)(14). The cell wall of M. tuberculosis plays a critical role in the defense of this pathogen in the host, since environmental stimuli induce changes in cell wall composition and thus help M. tuberculosis to adapt during infection (15,16).…”