EFFECT OF MUTATIONAL ALTERATION OF ASN-128 IN THE PUTATIVE GTP-BINDING DOMAIN OF TETRACYCLINE RESISTANCE DETERMINANT TET(O) FROM CAMPYLOBACTER-JEJUNI

The deduced amino acid sequence of Campylobacter jejuni Tet(O), cloned in Escherichia coli, has shown that it contains the five highly conse rved sequences of the GTP-binding domain found in other GTPases. Asn-1 28 belongs to the G4 motif of such a domain and is involved in hydroge n bonding with the guanine ring of the nucleotide. Substitution of Asn -128 by 11 other amino acids resulted in a decrease in tetracycline re sistance, indicating that tetracycline resistance conferred by Tet(O) is related to GTP binding. The effect of the mutations on the GTP-bind ing domain is discussed with the EF-Tn-GDP complex as a model.