title: Comparative nucleotide sequences encoding the immunity proteins and the carboxyl-terminal peptides of colicins E2 and E3.
abstract: Using the M13 dideoxy sequencing technique, we have established the DNA sequences of colicins E2 and E3 which encompass the receptor-binding and the catalytic domains of each of the nucleases, and their immunity (imm) genes. The imm gene of plasmid ColE2-P9 is 255 bp long and is separated from the end of the col gene by a dinucleotide. This gene pair is arranged similarly in plasmid ColE3-CA38 except that the intergenic space is 9 bp and the E3 imm gene is one codon shorter than its E2 counterpart. Comparisons of the E2 and E3 imm sequences indicate considerable divergence whereas the receptor-binding domains of both colicins are highly conserved. The two nuclease domains appear to share some sequence homology. A possible evolutionary relationship between colicin E3 and other microbial extracellular ribonucleases is also suggested from the sequence alignment analysis.
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D003087:Colicins / Q000235:genetics*; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000276:immunology; D029968:Escherichia coli Proteins; D005796:Genes; D005798:Genes, Bacterial; D010957:Plasmids
chemical_list: D001426:Bacterial Proteins; D003087:Colicins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C488855:ceiC protein, E coli; C007104:colicin immunity proteins; D004262:DNA Restriction Enzymes