PKCε inhibits the insulin receptor kinase by phosphorylating a threonine residue near the catalytic domain's activation tyrosines, conserved from humans to fruit flies.

“when you add activated epsilon to the receptor you phosphorylate this threonine and that got us very excited because kali that's one amino acid away from these two tyrosines that are required for activation receptors may be doing something important and so the other thing that got us excited about and here's getting into evolution is the sequence of the catalytic domain for the receptor and it's been conserved all the way from humans down to fruit flies”