title: Sequence, expression and localization of the immunity protein for colicin B.
abstract: Cells of Escherichia coli containing the cbi locus on plasmids are immune to colicin B which kills cells by dissipating the membrane potential through pore formation in the cytoplasmic membrane. The nucleotide sequence of the cbi region was determined. It contains an open reading frame for a polypeptide consisting of 175 amino acids. The amino acid sequence is homologous to the primary structure of the colicin A immunity protein. This, and the strong homology between the pore-forming domains of colicins A and B suggests a common evolutionary origin for both colicins. The immunity protein could be identified following strong overexpression of cbi. The electrophoretically determined molecular weight of 20,000 was close to the calculated molecular weight of 20,185. The protein contains four large hydrophobic regions. The immunity protein was localized in the membrane fraction and was mainly contained in the cytoplasmic membrane. It is proposed that the immunity protein inactivates the colicin in the cytoplasmic membrane.
authors.affiliation: Mikrobiologie II, Universität Tübingen, Federal Republic of Germany.
authors.forename: E
authors.initials: E
authors.lastname: Schramm
authors.forename: T
authors.initials: T
authors.lastname: Olschläger
authors.forename: W
authors.initials: W
authors.lastname: Tröger
authors.forename: V
authors.initials: V
authors.lastname: Braun
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002451:Cell Compartmentation; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003087:Colicins / Q000037:antagonists & inhibitors*; D004262:DNA Restriction Enzymes; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005786:Gene Expression Regulation; D005796:Genes; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012995:Solubility
chemical_list: D001426:Bacterial Proteins; C488854:Cbi protein, E coli; D003087:Colicins; D029968:Escherichia coli Proteins; C007104:colicin immunity proteins; D004262:DNA Restriction Enzymes