 RHEB acts as an activator for mTORC1 in its GTP-bound form, therefore GTP-bound RHEB activates cell growth and proliferation within the cell.RHEB can serve as a regulator, for other proteins independent from mTORC1.For example, RHEB is an activator for nucleotide synthesis by binding carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, and dihydroorotase (CAD), an enzyme required for "de novo" pyrimidine nucleotide synthesis.