LcrV is a channel size-determining component of the Yop effector translocon of Yersinia

Delivery of Yop effector proteins by pathogenic Yersinia across the eukaryo tic cell membrane requires LcrV, YopB and YopD. These proteins were also re quired for channel formation in infected erythrocytes and, using different osmolytes, the contact-dependent haemolysis assay was used to study channel size, Channels associated with LcrV were around 3 nm, whereas the homologo us PcrV protein of Pseudomonas aeruginosa induced channels of around 2 nm i n diameter. In lipid bilayer membranes, purified LcrV and PcrV induced a st epwise conductance increase of 3 nS and 1 nS, respectively, in 1 M KCl. The regions important for channel size were localized to amino acids 127-195 o f LcrV and to amino acids 106-173 of PcrV. The size of the channel correlat ed with the ability to translocate Yop effecters into host cells. We sugges t that LcrV is a size-determining structural component of the Yop transloco n.