Investigation of the specificity of the interaction between colicin E9 and its immunity protein by site-directed mutagenesis.
Comparison of the amino acid sequences of the C-terminal domain of three DNAase type E colicins has identified six candidate specificity determinants for the interaction of these E colicins with their homologous immunity proteins. We have changed these candidate specificity determinants of colicin E9, using site-directed mutagenesis, to the corresponding amino-acids of colicin E8. A 'mutant' colicin E9, in which four of the six candidate specificity determinants have been changed, demonstrated colicin activity against Escherichia coli indicator strains which carried either the E8imm or the E9imm genes, indicative of a 'novel' E. colicin. After changing all six of the candidate specificity determinants, the resulting colicin E9 'mutant' exhibited a phenotype very similar to that of colicin E8.
Curtis
M D
MD
Molecular/Microbiology Sector, School of Biological Sciences, University of East Anglia, Norwich, UK.
James
R
R
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D003086:Bacteriocin Plasmids / Q000235:genetics*; D001483:Base Sequence; D003087:Colicins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D011485:Protein Binding; D012689:Sequence Homology, Nucleic Acid
D001426:Bacterial Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; C007104:colicin immunity proteins; C488858:immE8 protein, E coli; C488859:immE9 protein, E coli