| Type: | Family | Name: | Macrophage infectivity potentiator |
| Description: | Legionella pneumophila, the causative agent of Legionnaire's disease, is a facultative intracellular microbe that commonly infects human lung monocytes and macrophages and causes pneumonia []. It is water-borne and highly virulent, relying on several specific pathogenic factors to invade and infect the alveolar tissue. However, once grown to stationary phase in culture, the pathogen spontaneously converts to an avirulent state []. The major virulence factor expressed by Legionella pneumophilais the macrophage infectivity potentiator (Mip) []. Site-directed mutagenesis studies of this protein in vitro severely impaired the intracellular infection of human macrophages by L. pneumophila, causing it to lose its potent antigenic activity []. Further studies into the enzymatic activity of Mip have revealed that it plays a similar role to eukaryotic FK506-binding proteins. In vivo, it acts as a peptidyl-prolyl-cis/trans- isomerase (PPIase) on oligopeptides [], although it is unclear whether this forms part of the virulence process. Substitution of Asp142 of the mature protein by Leu severely reduces the PPIase activity of Mip []. The structure of Mip has been resolved to 2.41A by X-ray crystallography [], revealing the virulence factor to exist as a homodimer. Each monomer consists of an N-terminal dimerisation module, a long central connecting alpha-helix and a conserved PPIase domain at the C terminus. | Short Name: | INFPOTNTIATR |
