Cooperative evolution of mechanisms of β-lactam resistance A.A. Medeiros  Clinical Microbiology and Infection  Volume 6, Pages 27-33 (January 2000) DOI: 10.1111/j.1469-0691.2000.tb02037.x Copyright © 2000 European Society of Clinical Infectious Diseases Terms and Conditions

Figure 1 Cartoon showing entry of a β-lactam molecule into the active site cavity of a β-lactamase, hydrolysis of the β-lactam ring end release of the inactivated β-lectam (from [11]). Clinical Microbiology and Infection 2000 6, 27-33DOI: (10.1111/j.1469-0691.2000.tb02037.x) Copyright © 2000 European Society of Clinical Infectious Diseases Terms and Conditions

Figure 2 Space filling model of the active site cavity of S. aureus PC1 β-lactamase (from [12]). Clinical Microbiology and Infection 2000 6, 27-33DOI: (10.1111/j.1469-0691.2000.tb02037.x) Copyright © 2000 European Society of Clinical Infectious Diseases Terms and Conditions

Figure 3 Ribbon diagram of the TEM-1 β-lactamase. (Provided by Jim Knox, from [1].) Clinical Microbiology and Infection 2000 6, 27-33DOI: (10.1111/j.1469-0691.2000.tb02037.x) Copyright © 2000 European Society of Clinical Infectious Diseases Terms and Conditions

Figure 4 (A) Schematic diagram showing the hydrogen bonding network and the amino acid residues of the binding site motifs of a class A β-lactamase. Note the importance of residues E166 and N170 of the omega loop in positioning a water molecule close to sarine-70. (B) Hydrogen bond interactions between the functional groups of a cephalosporin molecule and the side-chains of the amino acid residues of the active site. Note that the NH groups of S70 and A237 hold the carbonyl of the β-lactam ring in the oxyanion pocket. The side-chains of S130 and T235 anchor one end of the molecule and those of N132 and A237 anchor the other (from [1]). Clinical Microbiology and Infection 2000 6, 27-33DOI: (10.1111/j.1469-0691.2000.tb02037.x) Copyright © 2000 European Society of Clinical Infectious Diseases Terms and Conditions

Figure 5 (A) Ceftazidime in the binding site of TEM-12 (R164S). The broken line between E166 and N170 represents a loosened, more flexible omega loop caused by the R164S mutation that weakens the bonding between R164 and N179 across the neck of the loop (not shown in this diagram). This provides more room for the bulky substituent of ceftazidime. Note that negatively charged side-chains of E104 and E240 repel the terminal carboxyl of the substituent. (B) Ceftazidime in the binding site of TEM-26 (R164S and E104K). The longer, more flexible side-chain of lysine bonds with the carboxyl moiety of the ceftazidime substituent providing an additional anchor (from [1]). Clinical Microbiology and Infection 2000 6, 27-33DOI: (10.1111/j.1469-0691.2000.tb02037.x) Copyright © 2000 European Society of Clinical Infectious Diseases Terms and Conditions