The serine/threonine protein phosphatase PstP of Mycobacterium

Regarded at this time being to be the only serine/threonine phosphatase acting to oppose the activity of eleven serine/threonine protein kinases in Mycobacterium tuberculosis, PstP is a highly active enzyme that could potentially dephosphorylate more than 500 serine/threonine protein phosphorylation sites identified so far in the M. tuberculosis proteome. Located in a genetic locus with genes encoding serine/threonine protein kinases PknA and PknB, PstP is probably involved in controlling mycobacterial cell growth and is conserved in Mycobacteria and other Actinobacteria.

To study the function of PstP, a strain of Mycobacterium smegmatis with conditional expression of the pstP operon was characterised for its growth and morphological phenotypes and phosphoproteome. The changes to cell wall and septum during pstP knockdown, and increases in phosphorylation of PknB and PknB-substrates, support the hypothesis that PstP regulates cell wall biosynthesis and cell division, potentially via PknB. However, the phosphoproteome's broad changes may also indicate a more extensive role of PstP as a negative global regulator of serine-threonine protein phosphorylation.