Sequences of the Genes for the TEM-20, TEM-21, TEM-22, and TEM-29 Extended-Spectrum β-Lactamases

The sequences of thebla TEM genes encoding TEM-20, TEM-21, TEM-22, and TEM-29 extended-spectrum β-lactamases were determined. Analysis of the deduced amino acid sequences indicated that TEM-20 and TEM-29 were derived from TEM-1 and that TEM-21 and TEM-22 were derived from TEM-2. The substitutions involved were Ser-238 and Thr-182 for TEM-20; His-164 for TEM-29; Lys-104, Arg-153, and Ser-238 for TEM-21; and Lys-104, Gly-237, and Ser-238 for TEM-22. The promoter region of thebla TEM-22 gene was identical to that ofbla TEM-3 . High-level production of TEM-20 could result from a 135-bp deletion which combined the −35 region of thePa promoter with the −10 region of theP3 promoter and a G→T transition in the latter motif.