This family of proteins contains MlaD, which is a component of the Mla pathway, an ABC transport system that functions to maintain the asymmetry of the outer membrane [1]. The family also contains the mce (mammalian cell entry) proteins from Mycobacterium tuberculosis. The archetype (Rv0169), was isolated as being necessary for colonisation of, and survival within, the macrophage [2]. This family contains proteins of unknown function from other bacteria.

1: An ABC transport system that maintains lipid asymmetry in the gram-negative outer membrane. Malinverni JC, Silhavy TJ; Proc Natl Acad Sci U S A. 2009;106:8009-8014. PMID:19383799

2: Cloning of an M. tuberculosis DNA fragment associated with entry and survival inside cells [see comments] Arruda S, Bomfim G, Knights R, Huima-Byron T, Riley LW; Science 1993;261:1454-1457. PMID:8367727

3: Disruption of the mycobacterial cell entry gene of Mycobacterium bovis BCG results in a mutant that exhibits a reduced invasiveness for epithelial cells. Flesselles B, Anand NN, Remani J, Loosmore SM, Klein MH; FEMS Microbiol Lett 1999;177:237-242. PMID:10474190