In vitro tyrosine phosphorylation studies on RAS proteins and calmodulin suggest that polylysine-like basic peptides or domains may be involved in interactions between insulin receptor kinase and its substrate.

We have investigated the in vitro tyrosine phosphorylation of the HRAS and KRAS proteins by human placental insulin receptor kinase. Purified HRAS proteins are not phosphorylated by purified insulin receptor kinase. Since the tyrosine phosphorylation of calmodulin by the insulin receptor kinase in vitro requires cofactors such as protamine and poly(L-lysine… CONTINUE READING