The mammalian target of rapamycin (mTOR), a protein kinase, is the centre of huge attention due to its importance in intracellular signaling and in health and disease.In their recent study, Yin et al.show that mTOR can regulate signaling through the insulin-like growth factor 1 receptor and that it possesses a new enzymatic activity-the ability to phosphorylate proteins on tyrosine residues.