ENERGY-DEPENDENT RECEPTOR ACTIVITIES OF ESCHERICHIA-COLI K-12 - MUTATED TONB PROTEINS ALTER FHUA RECEPTOR ACTIVITIES TO PHAGES T5, T1, PHI-80 AND TO COLICIN-M

The activity of the FhuA receptor in the outer membrane of Escherichia coli is dependent on the TonB, ExbB and ExbD proteins which are ancho red to the cytoplasmic membrane. Only infection by phage T5 occurs ind ependently of TonB, ExbB and ExbD. In this paper we describe mutated F huA proteins which displayed either an increased or decreased FhuA act ivity to phage. T5 when combined with mutated TonB proteins. These res ults suggest conformational changes in FhuA by TonB which are recogniz ed by phage T5. Similar results were obtained with colicin M and the p hages T1 and phi 80. It is proposed that the FhuA mutant proteins assu me conformations which are either improved or impaired by the TonB der ivatives. For the direct interaction of FhuA with TonB regions which a re located outside the TonB box of FhuA and the region around residue 160 of TonB are important.