PrkC-mediated phosphorylation of overexpressed YvcK regulates PBP1 localization in Bacillus subtilis mreB mutant cells [Microbiology]

July 10th, 2014 by Foulquier, E., Pompeo, F., Freton, C., Cordier, B., Grangeasse, C., Galinier, A.

The YvcK protein was shown to be necessary for growth in gluconeogenic conditions in Bacillus subtilis. Amazingly, its overproduction rescues growth and morphology defects of the actin-like protein MreB deletion mutant by restoration of PBP1 localization. In this paper, we observe that YvcK is phosphorylated on threonine 304 by the protein kinase PrkC and phosphorylated YvcK is dephosphorylated by the cognate phosphatase PrpC. We show that neither the substitution of this threonine by a constitutively phosphorylated mimicking glutamic acid residue or by a phosphorylation-dead mimicking alanine residue, nor the deletion of prkC alters the ability of B. subtilis to grow in gluconeogenic conditions. However, we observe that a prpC mutant as well as a yvcK mutant are more sensitive to bacitracin as compared to the WT strain. In addition, strains in which YvcK threonine 304 is replaced either by an alanine or by a glutamic acid residue are also affected in bacitracin sensitivity. We have also analyzed the rescue of the mreB mutant strain by overproduction of YvcK in which the phosphorylation site was substituted. We show that YvcK T304A overproduction does not rescue the mreB mutant aberrant morphology due to PBP1 mislocalization. The same observation has been made in an mreB prkC double mutant overproducing YvcK. Altogether, these data show that YvcK may have two distinct functions: one in carbon source utilization independently of its phosphorylation level and a second in cell wall biosynthesis and morphogenesis through its phosphorylation state.