Figure 5
Model for Stk-/Stp-dependent regulation of cell wall synthesis protein FemX. (a) During regular growth, the kinase Stk is not phosphorylated and less active. Hence, the phosphatase Stp dephosphorylates the Stk-target FemX and other cell wall synthesis enzymes. (b) Following cell growth arrest due to nutrient depletion, accumulated pentaglycine-lipid II activates Stk through PASTA domain-dependent binding9. Active Stk phosphorylates FemX and other cell wall synthesis enzymes, leading to downregulation of cell wall synthesis. (c) In the stp deletion strain, phosphorylated Stk-target proteins like FemX cannot be reversed by dephosphorylation and in consequence accumulate in the cell. This increases the concentration of PGN precursors and incomplete muropeptides are incorporated into the cell wall, resulting in a thicker cell wall and reduced lysostaphin sensitivity.
