A substrate-inspired probe monitors translocation, activation, and subcellular targeting of bacterial type III effector protease AvrPphB
Lu, Haibin × Wang, Zheming Shabab, Mohammed Oeljeklaus, Julian Verhelst, Steven Kaschani, Farnusch Kaiser, Markus Bogyo, Matthew van der Hoorn, Renier A L #
Current Biology Ltd.
Chemistry & Biology vol:20 issue:2 pages:168-76
The AvrPphB effector of Pseudomonas syringae is a papain-like protease that is injected into the host plant cell and cleaves specific kinases to disrupt immune signaling. Here, we used the unique substrate specificity of AvrPphB to generate a specific activity-based probe. This probe displays various AvrPphB isoforms in bacterial extracts, upon secretion and inside the host plant. We show that AvrPphB is secreted as a proprotease and that secretion requires the prodomain, but probably does not involve a pH-dependent unfolding mechanism. The prodomain removal is required for the ability of AvrPphB to trigger a hypersensitive cell death in resistant host plants, presumably since processing exposes a hidden acylation site required for subcellular targeting in the host cell. We detected two active isoforms of AvrPphB in planta, of which the major one localizes exclusively to membranes.