My major scientific interest is in Mammalian Cell biology. My research involved the use of protein toxins from bacteria and plants, which traffic inside cells , cross an intracellular membrane (either the endosome membrane , diphtheria toxin: or the endoplasmic reticulum membrane for Pseudomonas exotoxin A, Shiga toxin and ricin) initially to examine the intracellular routes they take during the intoxication process. However, following some genetic screens that identified mutants with partial resistance to these proteins, I became more interested in what happens to these proteins when they enter the cytosol of a mammalian cell. This led to a molecular dissection of the ER dislocon used to by the toxins to enter the cytosol and an examination of chaperone and proteasome interactions within the cytosol. Surprisingly, the proteasome, a destructive complex that degrades old and misfolded proteins does not degrade ricin, but instead maintains it in a folded condition: the proteasome is also a folding machine.