Team:Valencia/Project1

The Colicins

The Colicins are proteins produced by some strains of Escherichia coli that are lethal for related strains of E. coli. Colicins of strain CA46 (colicin G producer) and of strain CA58 (colicin H producer) should be the same, and indeed, the sensitivity patterns were nearly identical. Only the triple mutant receptors fepA cir fiu was completely resistant to the colicins from these strains.

(i) the production of colicin by colicinogenic E. coli cells is induced by SOS agents, as is seen with lysogenic phages, and is lethal for producing cells.

(ii) the produced colicin is released into the medium late after synthesis (later shown not to be the case for all colicins).

(iii) colicin kills sensitive cells according to single-hit kinetics.

(iv) colicin is not active against the producing bacteria due to the presence of a specific antagonist protein called the immunity protein.

All colicins are organized into three domains, each corresponding to one step of colicin action:

o The N-terminal domain is involved in translocation through the membrane.

o The central domain is involved in binding to the receptor.

o The C-terminal domain contains the active part.

The sequence of the colicin G and colicin H determinants have been deposited under the accession numbers AJ515251 and AJ515252, respectively, in the EMBL/GenBank database.

Escherichia coli microcin operon, strain CA46 (CA46 ColG) [http://www.ncbi.nlm.nih.gov/nuccore/AJ515251]

Escherichia coli microcin operon, strain CA58 (CA58 ColH) [http://www.ncbi.nlm.nih.gov/nuccore/AJ515252]