Characterization and Expression of a Cloned Tetracycline Resistance Determinant from Campylobacter Jejuni Plasmid PUA466

A tetracycline resistance (Tcr) determinant previously cloned from the Campylobacter jejuni plasmid pUA466 (D. E. Taylor, J. Bacteriol. 165:1037-1039, 1986) was localized by restriction endonuclease mapping, subcloning, and Tn1000 insertion mutagenesis to a 2-kilobase region consisting of 1.8- and 0.2-kilobase HincII fragments. Tcr encoded by the cloned fragment (pUOA1) was expressed constitutively in Escherichia coli. A protein with an apparent molecular weight of 68,000 encoded by pUOA1 was produced in an in vitro transcription-translation system and in minicells. Tn1000 insertions which resulted in inactivation of Tcr expression also resulted in an alteration in the 68,000-molecular-weight protein. Some mutants specified a truncated protein, whereas others completely lost the ability to specify the protein. The protein which appears to be involved in the expression of Tcr specified by C. jejuni plasmids is of approximately the same molecular weight as the protein specified by the streptococcal class M determinant. This finding is consistent with our previous results which indicate that homology exists between the Tcr determinant from C. jejuni and a 5-kilobase HincII probe derived from the streptococcal class M determinant.