Article Figures & Data
Figures
- Fig. 1.
TEM-1 β-lactamase with clavulanic acid bound in the active site. The side chains of the residues Met69, Ser130, Arg244, and Asn276 are shown as a ball and stick representation; Clav, clavulanic acid. The figure was prepared by using the MOLSCRIPT program (17).
- Fig. 2.
(A) Preacylation complex of TEM-1 β-lactamase and clavulanic acid. (B) The active site is shown for the regions within the vicinity of the acyl-enzyme intermediate of TEM-1 β-lactamase and clavulanic acid. Clavulanic acid (Clav), water molecules, and Ser70 are shown as ball and stick representations. The arrow indicates the B3 strand, which forms a portion of the active-site surface. The figure was prepared by using the MOLSCRIPT program (17).
Tables
- Table 1.
Types of mutant β-lactamases selected by growth of transformants in the presence of ampicillin plus clavulanate
Mutant typea Amino acidb substitutions for the following amino acids of the wild-type TEM-1 β-lactamase: Silent mutation(s)c A42 N52 M69d K111 S130 H153 K192 T195 L201 G238 R244 T272 N276 1 N52Y M69L T272A A42A, T281T 2 M69L K192R R9R, Q206Q 3 S130G 4 A42G S130G T195A G238S T265T 5 R244C 6 A42G L201P R244C L73L 7 A42G H153D R244C R9R, K34K, L49L, R61R, Q88Q, K111K 8 A42G K111R L201P R244C R9R, K34K, L49L, R61R, G87G, I260I 9 R244S G45G, P257P 10 L201P R244S R65R, P67P, I260I 11 N276D ↵a The wild type is TEM-1.
↵b Amino acids are indicated by conventional single-letter nomenclature.
↵c Mutations in the base sequence of the gene that do not alter the amino acid sequence of the enzyme.
↵d The boldface font indicates sites at which mutations have previously been reported to confer resistance to β-lactam–clavulanate combinations.
- Table 2.
MICs of ampicillin, β-lactam inhibitors, and their combinations conferred by the TEM-1 β-lactamase and various types of mutant derivatives for E. coli JM83
β-Lactamase or mutant derivative MIC (μg/ml)a Ap Cl Ap + Cl 1b Ap + Cl 2 Ap + Cl 5 Ap + Cl 10 Sb Ap + Sb 5 Ap + Sb 10 Ap + Sb 20 Tb Ap + Tb 5 Ap + Tb 10 Ap + Tb 50 −c 4 32 4 4 4 2 32 2 1 NG 256 4 4 4 TEM-1 16,000 32 250 125 64 16 64 16,000 8,000 4,000 256 32 16 4 1 8,000 32 1,000 500 250 125 32 4,000 2,000 NG 256 64 32 4 3 1,000 32 1,000 1,000 500 250 32 250 64 NG 256 125 64 16 4 500 32 500 500 250 125 32 125 32 NG 256 125 64 16 5 2,000 32 2,000 1,000 500 125 32 500 125 NG 256 64 32 8 6 2,000 32 2,000 1,000 500 125 32 500 125 NG 256 125 64 8 7 500 32 500 250 125 64 32 125 32 NG 256 32 16 4 8 2,000 32 2,000 1,000 500 125 32 500 125 NG 256 125 64 8 9 8,000 32 4,000 2,000 1,000 250 32 2,000 500 NG 256 500 64 8 10 2,000 32 2,000 1,000 500 125 32 500 125 NG 256 64 32 8 11 16,000 32 4,000 2,000 1,000 250 64 16,000 16,000 8,000 256 2,000 64 8 ↵a Abbreviations: Ap, ampicillin; Cl, clavulanate; Sb, sulbactam; Tb, tazobactam.
↵b The numbers indicate the fixed concentration (in micrograms per milliliter) of the indicated inhibitor in combination with ampicillin for determination of ampicillin MICs.
↵c −, E. coli JM83 without a plasmid.
d NG, no growth in the presence of the lowest concentration of ampicillin tested (0.06 μg/ml for E. coliJM83 and 8 μg/ml for the transformants bearing a β-lactamase).
- Table 3.
MICs of cephalosporins and aztreonam conferred by TEM-1 β-lactamase and various types of mutant derivatives forE. coli JM83
β-Lactamase or mutant derivative MIC (μg/ml) Cephalothin Cephaloridine Ceftazidime Ceftriaxone Aztreonam −a 4 2 0.125 0.03 0.06 TEM-1 32 128 0.25 0.03 0.06 1 4 2 0.125 0.03 0.06 3 4 2 0.125 0.03 0.06 4 4 2 0.125 0.03 0.06 5 4 2 0.125 0.03 0.06 6 4 2 0.125 0.03 0.06 7 4 2 0.125 0.03 0.06 8 4 2 0.125 0.03 0.06 9 4 2 0.125 0.03 0.06 10 4 2 0.125 0.03 0.06 11 16 128 0.5 0.03 0.06 ↵a −, E. coli JM83 without a plasmid.
