Colicin El

The N-terminal portion of the 522-residue polypeptide chain of colicin El appears to be required for transport into the membrane and the central part for binding to the receptor the channelforming property is characteristic of the C-terminal region.k A similar organization has been established for the smaller colicin N translocation domain, (residues 1-66), receptor domain, (residues 67-182), and pore-forming domain (residues 183-387). 

The colicin El plasmid is a 4.43 MDa circular double stranded DNA molecule consisting of 6646 base pairs.1 Only one site is susceptible to cleavage by the restriction endonuclease ECoRl (Chapter 26) This feature has led to its widespread use in cloning of genes. 

Antisense RNA. Another mechanism of control of either transcription or of plasmid replication involves small molecules of RNA that are transcribed from the opposite strand than the template strand used for mRNA synthesis.1 13 165-166b These antisense RNA molecules have at least some part of their sequence complementary to that of the mRNA and to the corresponding sequence in DNA. A well-studied example is control of the copy number of the colicin El and other plasmids of E. co/i.167-169 Two transcripts, RNAI and RNAII, are initiated upstream from the origin of replication (Fig. 28-8). RNA II is a 555-nucleotide primer of replication. It is synthesized as a longer transcript that is cut by RNase H at ori. This... 

The existence of voltage-gated ion channels in bilayers are not limited to nerve membranes. They are present to some extent in all cell membranes. Even the paramecium has at least seven kinds of Na+, K+, and Ca2+ channels.483 Channels may also be formed by many peptide antibiotics. Among them are the human defensins (Chapter 31) and the 20-residue alamethi-cin. Six to eleven of the mostly helical monomers of that antibiotic assemble to form a single voltage-dependent channel.4844843 The bacterial toxin colicin El (Box 8-D) forms voltage-dependent channels within bacterial membranes.485... 

The naming of plasmids is generally haphazard. Some, e.g. plasmid Col El (pCol El) carries, as the name implies, immunity to colicin El. The majority, e.g. pMB9, pBR322, pACYC184 etc., are usually named after the initials of their discoverer (or engineer). 

ImmEI—immune to colicin El, Ap —ampicillin-resistant, CmR—chloramphenicol resistance, Km —kanamycin-resistant, Tc —tetracycline-resistant. 

Strawbridge. K.B. Palmer. L.R. Memll, A.R. Hallett, F.R. Integrated light-scattering spectroscopy, a sensitive probe for peptide-vesicle binding—Application to the membrane-bound colicin El channel peptide. Biophys. J. 

Colicin El is a 522-residue polypeptide ich is lethal to strains of E. coti that do not contain the re tance plasmid. Colicin El exeits its toxic effects by forming a channel in the cyto 4asmic metribrane which depolarizes and deenergizes the cell. The active channel forming domain consists... 

Figure 8.20. Stcm-M mer plots for aci amideqiienchii of MATA (x) end thtee siQ e-trypfajphaii mutants of the ctkaonel-forming peptide of colicin El, W-3SS ( ). W-460 (A), and W-443 (i9> Revised finm Ref. 48.

Colicin El from E.coli) [11032-88-5], Mr 56,000, pi 9.5. Colicin El is purified (8.6-fold to Specific Activity of 1.5 X 10 units/mg) from E. coli JC411 by salt extraction of extracellular-bound colicin followed by (NH4)2S04 (40-60% saturation) fractionation and ion-exchange chromatography on a DEAE-Sephadex A 50 column, and then by CM-Sephadex column chromatography [Schwartz Helinski J5to/ Chem 246 6318 7977]. 

A Sephadex cyclic imidocarbonate derivative reacted with colicins El, E2, and E3 to give products that were used to investigate the reactivities of colicins with cells. ... 

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