4.A.2.1.5
The mannitol porter (MtlA) (mannitol-1-P forming), MtlAF.  The system is encoded by the mannitol catabolic operon, mtlAFD, and is regulated by the transcription factor, MtlR (Joyet et al. 2015). MtlR contains an N-terminal helix-turn-helix motif followed by an Mga-like domain, two PTS regulatory domains (PRDs), an Enzyme IIB^Gat-like domain and an Enzyme IIA^Mtl-like domain, the last four of which can be phosphorylated by the PTS.  MtlR proteins are also found in Geobacillus stearothermophilus and Lactobacillus casei, but the mechanisms of their action are different (Joyet et al. 2015).  The dephosphorlyated form of the protein activates transcription (Heravi and Altenbuchner 2014).