The YopR core domain, predominantly found in the Gammaproteobacteria virulence factor YopR, is composed of five alpha-helices, four of which are arranged in an antiparallel bundle. Little is known about this domain, though it may contribute to the virulence of the protein YopR [1]. YopR controls the selective access of early (YscF, YscI and YscP) substrates to the type III secretion machines of yersiniae and other Gammaproteobacteriae. YopR is a mobile regulatory component thought to function as a checkpoints probing the completion of discrete intermediary stages in the assembly of the type III injection pathway. The location of secreted YopR (into the medium) is directly controlling the secretion of YscF, the polymerised needle protein Pfam:PF09392, thereby impacting the assembly of type III machines [2].

1: Crystal structure of the protease-resistant core domain of Yersinia pestis virulence factor YopR. Schubot FD, Cherry S, Austin BP, Tropea JE, Waugh DS; Protein Sci. 2005;14:1679-1683. PMID:15930010

2: YopR impacts type III needle polymerization in Yersinia species. Blaylock B, Berube BJ, Schneewind O; Mol Microbiol. 2010;75:221-229. PMID:19968786