The Yersinia effector YopJ inhibits the innate immune response by blocking MAP kinase and NFkappaB signaling pathways. YopJ is a serine/threonine acetyltransferase which regulates signalling pathways by blocking phosphorylation [1][2]. Specifically, YopJ has been shown to block phosphorylation of active site residues [3]. It has also been shown that YopJ acetyltransferase is activated by eukaryotic host cell inositol hexakisphosphate [4]. This family was previously incorrectly annotated in Pfam as being a peptidase family.

1: Yersinia YopJ acetylates and inhibits kinase activation by blocking phosphorylation. Mukherjee S, Keitany G, Li Y, Wang Y, Ball HL, Goldsmith EJ, Orth K; Science. 2006;312:1211-1214. PMID:16728640

2: Yersinia effector YopJ inhibits yeast MAPK signaling pathways by an evolutionarily conserved mechanism. Yoon S, Liu Z, Eyobo Y, Orth K; J Biol Chem. 2003;278:2131-2135. PMID:12433923

3: Acetylation of MEK2 and I kappa B kinase (IKK) activation loop residues by YopJ inhibits signaling. Mittal R, Peak-Chew SY, McMahon HT; Proc Natl Acad Sci U S A. 2006;103:18574-18579. PMID:17116858

4: The acetyltransferase activity of the bacterial toxin YopJ of Yersinia is activated by eukaryotic host cell inositol hexakisphosphate. Mittal R, Peak-Chew SY, Sade RS, Vallis Y, McMahon HT; J Biol Chem. 2010; [Epub ahead of print] PMID:20430892

5: Serine/threonine acetylation of TGFbeta-activated kinase (TAK1) by Yersinia pestis YopJ inhibits innate immune signaling. Paquette N, Conlon J, Sweet C, Rus F, Wilson L, Pereira A, Rosadini CV, Goutagny N, Weber AN, Lane WS, Shaffer SA, Maniatis S, Fitzgerald KA, Stuart L, Silverman N; Proc Natl Acad Sci U S A. 2012;109:12710-12715. PMID:22802624