In vivo evidence for FhuA outer membrane receptor interaction with the TonB inner membrane protein of Escherichia coli.

FhuA outer membrane receptor activity of Escherichia coli K-12 depends on the TonB inner membrane protein. The naturally occurring degradation of the TonB protein could be prevented by the FhuA receptor protein. Mutated TonB proteins could only be stabilized by mutated FhuA proteins when they functionally interacted in the uptake of ferrichrome across the outer membrane.