Phosphorothioate analogs of P1,P3-di(nucleosid-5′-yl) triphosphates: Synthesis, assignment of the absolute configuration at P-atoms and P-stereodependent recognition by Fhit hydrolase

New interactions between tumor suppressor Fhit protein and a nonhydrolyzable analog of its AP4 A substrate

Fragile histidine triad protein (Fhit) is a protein which primarily hydrolyses dinucleoside polyphosphates. To investigate possible interactions between the protein and a substrate, we used a nonhydrolyzable phosphorothioate analog of Ap₄ A, containing 5-bromo-2'-deoxyuridine instead of one adenosine residue. Photocrosslinking, followed by LC-MS experiments, determined a complex in which the probe was covalently linked to the NDSIYEELQK peptide (residues 110-119). The peptide was located within the 'disordered' region, which is invisible in the known crystal structures of Fhit. This invisible and flexible part seems to play a role in the stabilization of the Fhit-substrate complex, which may be important for its tumor suppressor activity.