InterPro domain: IPR042245

This superfamily includes toluene tolerance protein Ttg2 and intermembrane phospholipid transport system binding protein MlaC.

MlaC is a component of the Mla pathway, an ABC transport system that functions to maintain the asymmetry of the outer membrane. These proteins are involved in toluene tolerance, which is mediated by increased cell membrane rigidity resulting from changes in fatty acid and phospholipid compositions, exclusion of toluene from the cell membrane, and removal of intracellular toluene by degradation [ 1 ]. Ttg2 is one of the many proteins involved in these processes [ 2 ].

MlaC actively prevents phospholipid accumulation at the cell surface. It probably maintains lipid asymmetry in the outer membrane by retrograde trafficking of phospholipids from the outer membrane to the inner membrane. It may transfer phospholipids across the periplasmic space and deliver them to the mlaFEDB complex at the inner membrane [ 3 ].

1. Mechanisms for solvent tolerance in bacteria. J. Biol. Chem. 272, 3887-90
2. Isolation and characterization of toluene-sensitive mutants from the toluene-resistant bacterium Pseudomonas putida GM73. J. Bacteriol. 180, 3692-6
3. An ABC transport system that maintains lipid asymmetry in the gram-negative outer membrane. Proc. Natl. Acad. Sci. U.S.A. 106, 8009-14