Deletion mutations conferring substrate spectrum extension in the class A β-lactamase

Area of Science:

• Microbiology
• Enzymology
• Molecular Biology

Background:

• Beta-lactamase enzymes, like PenA, are crucial in bacterial resistance to antibiotics.
• Understanding mutations in beta-lactamases is key to combating antibiotic resistance.
• Burkholderia thailandensis is a relevant model organism for studying bacterial genetics.

Purpose of the Study:

• To characterize novel deletion mutations in the class A beta-lactamase PenA.
• To investigate the impact of these mutations on the enzyme's substrate spectrum and binding cavity flexibility.
• To explore the evolutionary pathways of beta-lactamases and their potential clinical implications.

Main Methods:

• Genetic analysis of Burkholderia thailandensis to identify deletion mutations.
• Enzymatic assays to determine the substrate spectrum of mutant PenA enzymes.
• Structural analysis to assess changes in the binding cavity flexibility.

Main Results:

• Four distinct deletion mutations (T171del, I173del, P174del, R165_T167delinsP) were identified in the PenA omega loop.
• These mutations significantly increased the flexibility of the enzyme's binding cavity.
• The modified PenA enzymes exhibited an extended substrate spectrum.

Conclusions:

• Deletion mutations in the PenA omega loop can confer an extended substrate spectrum.
• These findings offer insights into beta-lactamase evolution and potential mechanisms of antibiotic resistance.
• Such mutations could represent future threats for high-level ceftazidime resistance in clinical isolates.