Vitamin Gram-negative bacteria

Specific receptors for siderophores and vitamin B12 have been identified in the OM of Gram-negative bacteria. The translocation of these ligands across the outer membrane follows an energy-dependent mechanism and also involves the TonB, ExbB, ExbD proteins anchored in the cytoplasmic membrane. Biochemical and genetic data indicate that these proteins form a functional unit (the Ton complex), which couples the outer membrane receptor-mediated... 

Figure 1 Examples of several bacterial membrane proteins. The outer membrane (OM) of Gram-negative bacteria contains exclusively fS-barrel proteins, and three examples are shown BtuB (PDB ID 1NQF), which is the 22 p-stranded TonB-dependent active transporter for vitamin B 2/ th LamB or maltoporin trimer (PDB ID 1AF6), which is the 18 p-stranded passive sugar transporter and OmpA (PDB ID 1BXW), which is an 8 p-stranded protein that provides structural support for the OM. Proteins in the cytoplasmic membrane (CM) are helical, and three examples are shown the potassium channel KcsA (PDB ID 1BL8), which is a tetramer Sec YEG (PDB ID 1RH5), which forms the protein transport channel in Methanococcus and BtuCD (PDB ID ...

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