Interaction of dynamic sporulation protein SpoIIE with novel cell cycle regulator protein GpsB

K. Muchová, Z. Chromiková, I. Barák

Ústav Molekulárnej Biológie SAV, Dúbravská cesta 21, 84551 Bratislava, Slovakia

zuzana.chromikova@savba.sk

Spore formation is an ultimate response of Bacillus subtilis to hostile conditions. The process starts with an asymmetric cell division, at the onset of which dynamic sporulation protein SpoIIE has a key role in effecting the switch from normal mid-cell division to asymmetric division [1]. Asymmetric cell division requires the same set of division proteins as vegetative division. Both types of division require peptidoglycan synthesis to take place at the site of septation. Proteins involved in peptidoglycan synthesis are however also needed for the lateral cell growth, thus their trafficking between a division site and lateral cell wall must take place, depending on the stage of a cell cycle. One of the recently identified proteins, GpsB, operates in such shuttle system, transporting peptidoglycan synthesis protein PBP1 from a mature cell pole, which is a former division site, to the lateral cell wall. EzrA, on the other hand serves to return PBP1/GpsB complex back to the septum for division [2]. Very recently, GpsB was assigned with a role of general adaptor for peptidoglycan synthesizing enzymes PBPs, directing them to large protein complexes responsible for cell wall synthesis during cell elongation and cell division, facilitating thus these crucial interactions [3].

We demonstrated that GpsB interacts directly with SpoIIE and co-localizes with SpoIIE in the asymmetric septum, indicating that GpsB keeps its PBP-docking role also during asymmetric cell division.

We suggest that a multi-protein complex which includes sporulation specific SpoIIE and proteins involved in peptidoglycan synthesis (GpsB, EzrA, PBPs, RodZ) [4] may represent a direct link between asymmetric division and peptidoglycan biosynthesis.

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