Escherichia coli MRE 600 is a colicinogenic bacterium. Its colicinogenic activity may be ascribed mostly to colicin E1, although it produces a small amount of another, as yet unidentified, colicin.

The universal colicin-indicator strain Escherichia coli phi, unlike E. coli strain K-12, is sensitive to pesticin, a bacteriocin produced by wild-type Yersinia pestis. Eleven distinct phenotypes of E. coli phi mutants were obtained by selection for insensitivity to pesticin, group B colicins, the group A colicin S4, or coliphage T5. Representative isolates from eight of these classes closely re...

The Col Ib-P9 plasmid content of colicinogenic cells has been measured by both sedimentation analysis of cleared lysates and by deoxyribonucleic acid hybridization to purified Col Ib-P9 factor deoxyribonucleic acid. The results show an independence between mitomycin C-induced colicin synthesis and Col Ib-P9 replication. In addition, the ratio of the various molecular configurations (i.e., coval...

The immunity protein to colicin A (Cai), which is constitutively expressed at a very low level in Escherichia coli strains, has been studied in recombinant plasmid constructs allowing expression of various immunity fusion proteins under the control of inducible promoters. The 13-amino acid NH2-terminal region of Cai was substituted by polypeptides from beta-galactosidase or from colicin A. Upon...

Ribosomes that are synthesizing polypeptides in vitro on certain natural and synthetic messages are more susceptible to inactivation by colicin E3 than ribosomes treated with E3 in the absence of added message. The initiation step of protein synthesis appears to be sufficient to cause the conversion of ribosomes to a state more sensitive to colicin E3. Message and protein synthesis are not, how...

Cell-free protein synthesizing extracts incubated with purified preparations of colicin E(3) showed a marked decrease of their protein synthesizing activity. Incubation of ribosomes prepared from S-30 extracts with E(3) resulted in their inactivation. Their 16S RNA was found to lose a terminal fragment, similar in size to the fragment released upon in vivo treatment with E(3). Extracts derived ...

BACKGROUND Colicin E7 (ColE7) is one of the bacterial toxins classified as a DNase-type E-group colicin. The cytotoxic activity of a colicin in a colicin-producing cell can be counteracted by binding of the colicin to a highly specific immunity protein. This biological event is a good model system for the investigation of protein recognition. RESULTS The crystal structure of a one-to-one comp...

LexA protein is a repressor of several chromosomal genes involved in the SOS response in Escherichia coli. In previous experiments, we found that LexA protein may also be a repressor of the colicin E1 gene. We now present evidence that the purified LexA protein strongly repressed the in vitro transcription of the colicin E1 gene. As determined in DNase I protection experiments, LexA protein bou...

The region of the colicin E1 polypeptide that interacts with immunity protein has been localized to a 168-residue COOH-terminal peptide. This is the length of a proteolytically generated peptide fragment of colicin E1 against which imm+ function can be demonstrated in osmotically shocked cells. The role of particular amino acids of the COOH-terminal peptide in the expression of the immune pheno...

Pathway I. Group A nuclease colicins parasitize and bind tightly (Kd ≤ 10(-9) M) to the vitamin B12 receptor on which they diffuse laterally in the OM (outer membrane) and use their long (≥100 Å; 1 Å=0.1 nm) receptor-binding domain as a 'fishing pole' to locate the OmpF porin channel for translocation. Crystal structures of OmpF imply that a disordered N-terminal segment of the colicin T-domain...