B. Kenny et M. Jepson, Targeting of an enteropathogenic Escherichia coli (EPEC) effector protein to host mitochondria, CELL MICROB, 2(6), 2000, pp. 579-590
Many Gram-negative pathogens use a type III secretion apparatus to deliver
effector molecules into host cells to subvert cellular processes in favour
of the pathogen. Enteropathogenic Escherichia coli (EPEC) uses such a syste
m to deliver the Tir effector molecule into host cells. In this paper, we s
how that the gene upstream of tir, orf19, encodes an additional type III se
creted effector protein. Orf19 is delivered into host cells by a mechanism
independent of endocytosis, but dependent on EspB. Orf19 is targeted to hos
t mitochondria, where it appears to interfere with the ability to maintain
membrane potential. Although the precise role of Orf19 remains to be elucid
ated, its interaction with mitochondria suggests a possible role in the sub
version of key functions of these organelles, such as energy production or
control of cell death. This is the first example of a type III secreted pro
tein targeted to mitochondria; it is probable that homologues (present in E
PEC and Shigella species) and other bacterial effecters will also target th
is organelle.