'Holy' proteins II: the soluble lytic transglycosylase

Enzymes involved in the metabolism of the bacterial cell wall peptidoglycan are excellent targets for antibiotics. Penicillins and related beta-lactam antibiotics inhibit the enzymes that act on the peptide cross-links of the peptidoglycan. The X-ray structure of the transglycosylase revealed a two-layered ring of alpha-helices in a right-handed superhelical arrangement with a separate catalytic domain on top, which resembles the fold of goose-type lysozyme. Three sequence motifs were found that characterize the catalytic and substrate-binding sites in the enzyme. These motifs are present in a broad family of muramidases and chitinases.