Meticillin is a narrow-spectrum beta-lactam antibiotic of the penicillin class. It should not be confused with the antibiotic metacycline. In 2005 the name of the drug was changed from methicillin to meticillin in accordance with the International Pharmacopoeia guidelines. Like other beta-lactam antibiotics, meticillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linkage between the linear peptidoglycan polymer chains that make up a major component of the cell wall of Gram-positive bacteria. It does this by binding to and competitively inhibiting the transpeptidase enzyme used by bacteria to cross-link the peptide (D-alanyl-alanine) used in peptidoglycan synthesis. Meticillin and other beta-lactam antibiotics are structural analogs of D-alanyl-alanine, and the transpeptidase enzymes that bind to them are sometimes called penicillin-binding proteins (PBPs).
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