Nucleic Acids Research, 1984, Vol. 12, No. 22 8733-8745
© 1984
MOLECULAR BIOLOGY |
Comparative nucleotide sequences encoding the immunity proteins and the carboxyl-terminal peptides of colicins E2 and E3*
+Biomathematics, Division of Biological Sciences, National Research Council of Canada 100 Sussex Drive, Ottawa, Ontario K1A OR6, Canada Molecular Genetics Group, Division of Biological Sciences, National Research Council of Canada 100 Sussex Drive, Ottawa, Ontario K1A OR6, Canada
**To whom correspondence shoulde be addressed.
Received May 18, 1984. Revised October 18, 1984. Accepted October 18, 1984.
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.
*NRCC Publication No. 23865