Synthesis of gamma-[4-(benzoylphenyl)methylamido]-7-methylguanosine 5'-triphosphate, a photoaffinity-label for cap-binding proteins.

An easy and rapid method for the synthesis of the photoreactive cap analogue gamma-[4-(benzoylphenyl)methylamido]-7-methylguanosine-5'-triphosp hate (BP-m7GTP) has been developed. Synthesis of [gamma-32P]BP-m7GTP was carried out as a two-step procedure. The first step included the phosphorylation of GDP with [32P]orthophosphate to [gamma-32P]GTP and its methylation to [gamma-32P]m7GTP. After purification, [gamma-32P]m7GTP was condensed with 4-aminomethyl-benzophenone-HCl to [gamma-32P]BP-m7GTP. Using this probe, specific labeling of nuclear cap binding proteins is demonstrated.