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PmbA/TldA metallopeptidase domain 1 This entry represents a group of metalloproteases. The tertiary structure of the Escherichia coli TdlD/TdlE complex has been solved, and shows that the TdlD subunit is the active peptidase, binding a single zinc ion at an HEXXXH motif in which the glutamic acid is a substrate-binding residue and the two histidines are zinc ligands. The third zinc ligand is a cysteine, C-terminal to the HEXXXH motif. The TldE (also known as PmbA) by itself has no catalytic activity, does not bind zinc, and does not carry the HEXXXH motif. TldD and TldE were originally identified as regulators of DNA gyrase. Later, they are shown to be metalloproteases involved in CcdA degradation.
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