Fig. 5.

Model for RPS5 activation. Free RPS5 is unable to activate defense responses because of the negative regulatory action of the LRR domain. In the uninfected cell, most, if not all RPS5 is bound to PBS1 and ADP (D) and primed for a response to pathogen attack. PBS1 is cleaved through the cysteine protease action of AvrPphB after injection by P. syringae. PBS1 cleavage is detected by RPS5, resulting in a conformational change that enables exchange of ATP (T) for ADP. The ATP-bound form of RPS5 then engages downstream signaling molecules, activating the defense response.