Essential for the phosphorelay during initiation of sporulation. May control the level of phosphorylated spo0A through spo0E activity during sporulation. In the vegetative phase, localized throughout the periphery of the cell and the division septum. In the sporulation stages, fluorescence of the YaaT-GFP fusion protein was observed as two dots at the sides of an asymmetric septum and at the edges of the forespore.