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. Author manuscript; available in PMC: 2013 Feb 17.
Published in final edited form as: ACS Chem Biol. 2011 Dec 12;7(2):260–268. doi: 10.1021/cb2003913

Figure 4.

Figure 4

Hypothesized uptake mechanisms for methanobactin and copper. Copper (Cu) is transported across the outer membrane (OM) by a passive transport process likely involving porins whereas Cu-Mb is transported via an active process potentially mediated by TonB-dependent transporters (TBDTs). The mechanism of translocation across the inner membrane (IM) is unknown, but by analogy to siderophores, could involve an ATP-binding cassette (ABC) transporter and a periplasmic binding protein (PBP). It remains unclear whether intact Cu-Mb interacts directly with pMMO or with proteins involved in the “copper switch.”