Penicillin-binding proteins

Penicillin-binding proteins are bacterial enzymes that synthesize and remodel peptidoglycan, the mesh-like polymer that gives cell walls strength and shape. Many are targets of beta-lactam antibiotics.

Transpeptidase: An enzyme that forms peptide bonds between peptidoglycan strands by cross-linking their peptide side chains. Many penicillin-binding proteins cross-link peptidoglycan through this catalytic activity.
Beta-lactam antibiotics: Antibiotics containing a beta-lactam ring that inhibit bacterial cell-wall synthesis. They acylate susceptible penicillin-binding proteins and block peptidoglycan cross-linking.
Serine hydrolase: An enzyme class that uses an active-site serine to catalyze bond cleavage or formation. Many high-molecular-weight penicillin-binding proteins use an active-site serine in transpeptidation.
Alexander Fleming: A Scottish bacteriologist who discovered penicillin's antibacterial effect in 1928. His discovery led to the antibiotics that revealed these proteins as drug targets.
Antimicrobial resistance: The ability of microorganisms to survive exposure to drugs that would normally inhibit or kill them. Changes in penicillin-binding proteins are one route bacteria use to resist antibiotics.
Transglycosylase: An enzyme that joins sugar units into glycan chains in bacterial peptidoglycan. Some penicillin-binding proteins extend the glycan strands that transpeptidases later cross-link.
Penicillin: A beta-lactam antibiotic first isolated from Penicillium molds and used to treat bacterial infections. Penicillin's antibacterial action comes from inhibiting susceptible wall-building proteins.
Low-molecular-weight penicillin-binding protein: A class of penicillin-binding proteins that includes peptidoglycan carboxypeptidases and endopeptidases. These enzymes trim or rearrange wall peptides rather than building major cross-links.
Ernst Chain: A biochemist who helped develop penicillin into a therapeutic antibiotic during the 1930s and 1940s. Penicillin's clinical development made its bacterial targets a central research question.
MecA: A bacterial gene that encodes the altered penicillin-binding protein PBP2a in many MRSA strains. Its expression raises questions about how resistance proteins integrate with native wall synthesis.

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