Solid-state NMR spectroscopy was employed to study the molecular dynamics of the colicin Ia channel domain in the soluble and membrane-bound states. In the soluble state, the protein executes small-amplitude librations (with root-mean-square angular fluctuations of 0-10 degrees ) in the backbone and larger-amplitude motions (16-17 degrees ) in the side chains. Upon membrane binding, the motiona...

E3 colicinogenic cells are immune to colicin E3. A protein called "E3 immunity protein" was previously isolated from E3 colicinogenic cells and shown to prevent the E3-induced in vitro inactivation of ribosomes. We now show that the structural gene for E3 immunity protein resides on the Col E3 plasmid, a plasmid which is present in E3 colicinogenic cells and carries the structural gene for coli...

CvaB, a member of the ATP-binding cassette transporter superfamily, is the central membrane transporter of the colicin V secretion system in Escherichia coli. Cys32 and His105 in the N-terminal domain of CvaB were identified as critical residues for both colicin V secretion and cysteine proteolytic activity. By inhibiting degradation with N-ethylmaleimide and a mixture of protease inhibitors, a...

Natively unfolded proteins range from molten globules to disordered coils. They are abundant in eukaryotic genomes and commonly involved in molecular interactions. The essential N-terminal translocation domains of colicin toxins from Escherichia coli are disordered bacterial proteins that bind at least one protein of the Tol or Ton family. The colicin N translocation domain (ColN-(1-90)), which...

A series of colicin-tolerant (tol) mutants of Escherichia coli K-12, which adsorbed colicins but were not killed by them, were isolated and studied genetically and physiologically. Three major classes of mutants were found: tol II, tolerant to colicins A, E1, E2, E3, and K; tol III, tolerant to A, E2, E3, and K; and tol VIII, tolerant to E1 only. The sites of tol II and tol III mutations mapped...

Colicin E-resistant mutants were isolated in Escherichia coli K-12 which, although still apparently possessing the E receptor and adsorbing colicin, were nevertheless insensitive (refractory) to its effect. Eight phenotypic groups were obtained, but some mutants from three of these groups were all shown to map at gal, whereas a second refractory locus, giving resistance to El alone, mapped clos...

The ColE7 operon is an SOS response regulon, which encodes bacteriocin ColE7 to kill susceptible Escherichia coli and its related enterobacteria under conditions of stress. We have observed for the first time that polyamines confer limited resistance against ColE7 on E. coli cells. Thus, this study aims to investigate the role of polyamines in modulating the protective effect of the E. coli cel...

Biological containment is a genetic technique that programs dangerous organisms to grow only in the laboratory and to die in the natural environment. Auxotrophy for a substance not found in the natural environment is an ideal biological containment. Here, we constructed an Escherichia coli strain that cannot survive in the absence of the unnatural amino acid 3-iodo-L-tyrosine. This synthetic au...