Fig. 5. A schematic representation depicting exochelin import and export by M. smegmatis. An ExiT ABC transporter protein may export the deferri-exochelin. The ferri-exochelin is delivered to the plasma membrane's FxuA–B–C complex after being recognized by an unidentified protein (on the outer membrane, indicated in the image by a “?”; yet to be identified). Inside the cell envelope, ferri-exochelin may transfer iron to mycobactin or another type of high-affinity iron-binding molecule in the bacterial cell wall. An unidentified reductase reduced the ferric ions and released them for utilization. Further deferri-exochelin exported outside the cell.¹⁷³.