The Structure of Mlc Titration Factor A (MtfA/YeeI) Reveals a Prototypical Zinc Metallopeptidase Related to Anthrax Lethal Factor

MtfA ofEscherichia coli (formerly YeeI) was previously identified as a regulator of the phosphoenolpyruvate (PEP)-dependent:glucose phosphotransferase system. MtfA homolog proteins are highly conserved, especially among beta- and gammaproteobacteria. We determined the crystal structures of the full-length MtfA apoenzyme fromKlebsiella pneumoniae and its complex with zinc (holoenzyme) at 2.2 and 1.95 Å, respectively. MtfA contains a conserved H149 E150 XXH153 +E212 +Y205 metallopeptidase motif. The presence of zinc in the active site induces significant conformational changes in the region around Tyr205 compared to the conformation of the apoenzyme. Additionally, the zinc-bound MtfA structure is in a self-inhibitory conformation where a region that was disordered in the unliganded structure is now observed in the active site and a nonproductive state of the enzyme is formed. MtfA is related to the catalytic domain of the anthrax lethal factor and the Mop protein involved in the virulence ofVibrio cholerae , with conservation in both overall structure and in the residues around the active site. These results clearly provide support for MtfA as a prototypical zinc metallopeptidase (gluzincin clan).