Structure of a pathogen effector reveals the enzymatic mechanism of a novel acetyltransferase family

Abstract

Effectors secreted by the type III secretion system are essential for bacterial pathogenesis. Members of the Yersinia outer-protein J (YopJ) family of effectors found in diverse plant and animal pathogens depend on a protease-like catalytic triad to acetylate host proteins and produce virulence. However, the structural basis for this noncanonical acetyltransferase activity remains unknown. Here, we report the crystal structures of the YopJ effector HopZ1a, produced by the phytopathogen Pseudomonas syringae, in complex with the eukaryote-specific cofactor inositol hexakisphosphate (IP6) and/or coenzyme A (CoA). Structural, computational and functional characterizations reveal a catalytic core with a fold resembling that of ubiquitin-like cysteine proteases and an acetyl-CoA-binding pocket formed after IP6-induced structural rearrangements. Modeling-guided mutagenesis further identified key IP6-interacting residues of Salmonella effector AvrA that are required for acetylating its substrate. Our study reveals the structural basis of a novel class of acetyltransferases and the conserved allosteric regulation of YopJ effectors by IP6.

A bacterial acetyltransferase triggers immunity in Arabidopsis thaliana independent of hypersensitive response

“…Since the antibody (α-AcK) we used for testing HopZ5 autoacetylation did not allow us to detect non-lysine acetylation, additional autoacetylation of other residues in HopZ5 may still occur in both C218A and K278R variants. The crystal structure of HopZ1a revealed that the analogous residue to K278 in HopZ5, K211 in HopZ1a, is involved in coordination of the plant-derived cofactor IP6 20 . This suggests that HopZ5 K278 could also be involved in coordination of IP6 and thus loss of this residue in the K278R variant results in loss of acetylation activity.…”

“…syringae pv. syringae A2 autoacetylates a specific threonine residue (T346) with the involvement of two serine residues (S349 and S351) following in planta activation of HopZ1a by the plant cofactor IP6 20, 21 . In addition, HopZ1a acetylates jasmonate ZIM-domain (JAZ) repressors of jasmonic acid (JA) signalling leading to their proteosomal degradation, thereby activating the JA pathway and antagonizing salicylic acid-mediated disease resistance 22 .…”

Oh, the places they'll go! A survey of phytopathogen effectors and their host targets

“…cofactors). Examples include the activation of the AvrRpt2 protease by the eukaryotic cyclophilin, ROC1 (Coaker et al, 2005(Coaker et al, , 2006 and the activation of the HopZ1a acetyltransferase by phytic acid (Lee et al, 2012;Zhang et al, 2016). A third category includes 'sensor' targets that typically associate with NLR proteins, and promote ETI (Khan et al, 2016).…”

Foundational and Translational Research Opportunities to Improve Plant Health

“…In addition, effector biology has facilitated the discovery of biological processes. Examples of recently discerned effector biochemistries include: a newly identified mechanism of PTM (Zhang, Ma, et al 2016), novel PTMs (e.g. uridylation of several receptor like-cytoplasmic kinases by AvrAC, (Feng et al 2012); acetylation of histidines, (Lee et al 2015) and novel metabolites (Schuebel et al 2016).…”