TET(O), A PROTEIN THAT MEDIATES RIBOSOMAL PROTECTION TO TETRACYCLINE, BINDS, AND HYDROLYZES GTP

The tet(O) tetracycline resistance gene, originally cloned from Campylobacter-jejuni, mediates resistance by ribosomal protection. Using partially purified Tet(O) protein of 68 000 Da whose identity was verified by ribosomal protection assays, amino terminal sequencing, and immunoblotting using an antibody raised against the deduced 15 amino acids at the carboxyl terminus of the Tet(O) protein, the Tet(O) protein was found to bind to [alpha-P-32]GTP and [H-3]GDP using a filter binding assay. [gamma-P-32]GTP hydrolysis by Tet(O) was also demonstrated and was found to be time dependent with more than 50% of the hydrolysis activity occurring within the first 5 min. The GTPase activity of Tet(O) appears to be ribosome dependent, suggesting that ribosomes act as an effector similar to other G proteins involved in signal transduction.