Which antibiotic targets penicillin-binding proteins (PBPs)?

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Multiple Choice

Which antibiotic targets penicillin-binding proteins (PBPs)?

Penicillin-class antibiotics target penicillin-binding proteins, the enzymes that perform the final cross-linking steps in peptidoglycan synthesis of the bacterial cell wall. The beta-lactam ring of penicillins mimics the natural substrate D-Ala-D-Ala and binds to the active site of PBPs, effectively inactivating them. With PBPs stuck inactive, transpeptidation—and thus cross-link formation—stops, weakening the cell wall and causing the bacterium to lyse as it grows. Other options act at different targets: vancomycin binds to the D-Ala-D-Ala terminus of peptidoglycan precursors and blocks their incorporation, not the PBPs themselves. Ciprofloxacin inhibits DNA gyrase and topoisomerase IV, interfering with DNA replication. Tetracycline blocks the 30S ribosomal subunit, hindering protein synthesis. Because only penicillins directly inhibit PBPs, they are the correct choice.

Penicillin-class antibiotics target penicillin-binding proteins, the enzymes that perform the final cross-linking steps in peptidoglycan synthesis of the bacterial cell wall. The beta-lactam ring of penicillins mimics the natural substrate D-Ala-D-Ala and binds to the active site of PBPs, effectively inactivating them. With PBPs stuck inactive, transpeptidation—and thus cross-link formation—stops, weakening the cell wall and causing the bacterium to lyse as it grows.

Other options act at different targets: vancomycin binds to the D-Ala-D-Ala terminus of peptidoglycan precursors and blocks their incorporation, not the PBPs themselves. Ciprofloxacin inhibits DNA gyrase and topoisomerase IV, interfering with DNA replication. Tetracycline blocks the 30S ribosomal subunit, hindering protein synthesis. Because only penicillins directly inhibit PBPs, they are the correct choice.

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