9.B.138 The Putative Mycobacterial Outer Membrane Porin, LprG (LprG; P27) Family

The P27-P55 (lprG-Rv1410c) operon is crucial for the survival of Mycobacterium tuberculosis during infection in mice. P55 encodes an MFS efflux pump (2.A.1.3.34) that has been shown to provide Mycobacterium smegmatis and Mycobacterium bovis BCG with resistance to several drugs, while P27 encodes a mannosylated lipoglycoprotein, previously described as an antigen that modulates the immune response against mycobacteria.

P27 and P55 function together through an efflux-pump mechanism. Deletion of the P27-P55 operon made M. tuberculosis susceptible to sodium dodecyl sulfate, suggesting that the lack of these proteins causes alterations in the cell wall permeability of the bacterium. Both P27 and P55 are required to restore wild type drug resistance phenotypes in the mutant (Bianco et al., 2011; Farrow and Rubin, 2008). LprG and LppX have been suggested to function as carriers of lipids, glycolipids or their derviatives in outer membrane biogenesis (Luthra et al., 2011).