ATP5IF1 and cancer: However, we have documented the differential phosphorylation of IF1 in serine residues in cancer cells and in prevalent human carcinomas [27], and in different mouse tissues [28], and provided clear evidence that cAMP-dependent phosphorylation of S39 in IF1 by a PKA-like activity prevents the interaction of the inhibitory protein with the enzyme, whereas the dephosphorylated IF1 interacts and inhibits both ATP synthesis and hydrolysis by ATP synthase [27].