Role of Mycobacterium tuberculosis Ser/Thr Kinase PknF: Implications in Glucose Transport and Cell Division

Abstract

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 .