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Abstract

Tet() is an elongation factor-like protein found in clinical isolates of Campylobacter jejuni that confers resistance to the protein-synthesis inhibitor tetracycline. Tet() interacts with the 70S ribosome and promotes the release of bound tetracycline, however, as shown here, it does not form the same functional interaction with the 30S subunit. Chemical probing demonstrates that Tet() changes the reactivity of the 16S rRNA to dimethyl sulphate (DMS). These changes cluster within the decoding site, where C1214 is protected and A1408 is enhanced to DMS reactivity. C1214 is close to, but does not overlap, the primary tetracycline-binding site, whereas A1408 is in a region distinct from the Tet() binding site visualized by cryo-EM, indicating that Tet() induces long-range rearrangements that may mediate tetracycline resistance. Tetracycline enhances C1054 to DMS modification but this enhancement is inhibited in the presence of Tet() unlike the tetracycline-dependent protection of A892 which is unaffected by Tet(). C1054 is part of the primary binding site of tetracycline and A892 is part of the secondary binding site. Therefore, the results for the first time demonstrate that the primary tetracycline binding site is correlated with tetracycline's inhibitory effect on protein synthesis.