YSCN, THE PUTATIVE ENERGIZER OF THE YERSINIA YOP SECRETION MACHINERY

Pathogenic yersiniae secrete a set of 11 antihost proteins called Yops. Yop secretion appears as the archetype of the type III secretion pathway. Several components of this machinery are encoded by the virA (lcrA) and virC (lcrC) loci of the 70-kb pYV plasmid. In this paper, we describe yscN, another gene involved in this pathway. It is the first gene of the virB locus. It encodes a 47.8-kDa protein similar to the catalytic subunits of F,F, and related ATPases, as well as to products of other genes presumed to be involved in a type III secretion pathway. YscN contains the two consensus nucleotide-binding motifs (boxes A and B) described by Walker et al. (J. E. Walker, M. Saraste, M. J. Runswick, and N. J. Gay, EMBO J. 1:945-951, 1982). We engineered a pYV mutant encoding a modified YscN protein lacking box A. This mutant, impaired in Yop secretion, can be complemented in trans by a cloned yscN gene. We conclude that YscN is a component of the Yop secretion machinery using ATP. We hypothesize that it is either the energizer of this machinery or a part of it.