Part of an export system, which is required for biosynthesis and secretion of siderophores (PubMed:23431276). Essential for normal replication during the active-growth phase of the murine tuberculosis model (PubMed:15908378). Interacts with MmpS4. Transcriptionally regulated by MmpR5 (PubMed:24737322). Repressed by iron and IdeR (PubMed:12065475). Inactivation increases mouse survival. Belongs to the resistance-nodulation-cell division (RND) (TC 2.A.6) family. MmpL subfamily.