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Mol Microbiol. 1990 Dec;4(12):2027-33.

Vitamin B12 transport in Escherichia coli: energy coupling between membranes.

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Department of Microbiology, School of Medicine, University of Virginia, Charlottesville 22908.


Cells of Escherichia coli possess high-affinity active transport systems of vitamin B12 and iron-siderophore complexes. Specific outer-membrane proteins carry out the energy-dependent transport across the outer membrane, in conjunction with the TonB coupling protein. Mutagenesis experiments have identified a conserved region near the amino-terminus of the outer-membrane transporters that is necessary for energy-coupled transport. The ability of extragenic suppressor mutations in tonB to correct the transport defect indicates that TonB couples the proton-motive force to the outer-membrane proteins by direct contact.

[Indexed for MEDLINE]

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