CvaB is the central membrane transporter of the colicin V secretion system that belongs to an ATP-binding cassette superfamily. Previous data showed that the N-terminal and C-terminal domains of CvaB are essential for the function of CvaB. N-terminal domain of CvaB possesses Ca(2+)-dependent cysteine proteolytic activity, and two critical residues, Cys32 and His105, have been identified. In thi...

It has long been suggested that the import of nuclease colicins requires protein processing; however it had never been formally demonstrated. Here we show that two RNase colicins, E3 and D, which appropriate two different translocation machineries to cross the outer membrane (BtuB/Tol and FepA/TonB, respectively), undergo a processing step inside the cell that is essential to their killing acti...

We have studied the physiological effects of mitomycin C induction on cells carrying ColE1 plasmids with differing configurations of three genes: the structural gene coding for colicin (cea), a gene responsible for mitomycin C lethality (kil) that we located as part of an operon with cea, and the immunity (imm) gene, which lies near cea but is not in the same operon. kil is close to or overlaps...

Various catenated and replicating molecules of colicin E1 isolated from minicells have been identified in regions of neutral sucrose density gradients or cesium chloride-ethidium bromide density gradients. These colicin molecules have been found in those regions of the gradient where pulse-labeled DNA accumulates.

background: k99 pilus antigen is one of the major adherence factors found on enterotoxigenic escherichia coli (etec) of neonatal calves. it causes severe diarrhea in newborn calves via the production of heat-stable enterotoxin (sta).with increasing concern over the spread of antimicrobial resistance, the development of alternative to conventional antibiotics such as colicin is urgently needed. ...

Post-transcriptional regulation of gene expression plays a crucial role in many bacterial pathways. In particular, the translation of mRNA can be regulated by trans-acting, small, non-coding RNAs (sRNAs) or mRNA-binding proteins, each of which has been successfully treated theoretically using two-component models. An important system that includes a combination of these modes of post-transcript...

The interaction of colicins with target cells is a paradigm for protein import. To enter cells, bactericidal colicins parasitize Escherichia coli outer membrane receptors whose physiological purpose is the import of essential metabolites. Colicins E1 and E3 initially bind to the BtuB receptor, whose beta-barrel pore is occluded by an N-terminal globular "plug". The x-ray structure of a complex ...

Interaction of the TolB box of Group A colicins with the TolB protein in the periplasm of Escherichia coli cells promotes transport of the cytotoxic domain of the colicin across the cell envelope. The crystal structure of a complex between a 107-residue peptide (TA(1-107)) of the translocation domain of colicin A (ColA) and TolB identified the TolB box as a 12-residue peptide that folded into a...

We have used the antibiotics coumermycin A1, novobiocin, and oxolinic acid, which are specific inhibitors of DNA gyrase, to study the coupled transcription and translation of several bacterial and plasmid genes in a DNA-directed cell-free system. The expression of different genes is reduced to different extents by inhibition of DNA gyrase activity. Among the genes tested, the lac operon, an rRN...

Proteins conferring immunity against pore-forming colicins are localized in the Escherichia coli inner membrane. Their protective effects are mediated by direct interaction with the C-terminal domain of their cognate colicins. Cai, the immunity protein protecting E. coli against colicin A, contains four cysteine residues. We report cysteine cross-linking experiments showing that Cai forms homod...