A viral version of the Src kinase called v-Src is found in some retroviruses. Unlike the cellular Src, the v-Src kinase is constitutively active, and can drive the cell into uncontrolled growth and tumor formation. Which of the following molecular differences between the two versions of Src is more likely to be responsible for this?
A) v-Src lacks the active-site tyrosine residue.
B) v-Src lacks a lobe of the kinase domain.
C) v-Src has multiple inhibitory tyrosine phosphorylation sites in the kinase domain.
D) v-Src lacks the C-terminal tail that can bind to Src's SH2 domain.
E) v-Src has a longer C-terminal tail.