title: Topology and function of the integral membrane protein conferring immunity to colicin A.
abstract: The topology of the integral membrane protein Cai (colicin A immunity protein), which is required to protect producing cells from the pore-forming colicin A, was analysed using fusions to alkaline phosphatase. The properties of these fusion proteins support the model for Cai topology previously proposed on theoretical grounds. The protein was found to contain four transmembrane sequences and its N- and C-terminal regions were found to be directed towards the cytoplasm. Oligonucleotide-directed mutagenesis and sequence comparisons between Cai, Cbi (colicin B immunity protein), and Cni (colicin N immunity protein) were carried out to determine the functional regions of Cai. The possible roles of the various regions of Cai in its protective function and in its topological organization are discussed.
authors.affiliation: Centre de Biochimie et Biologie Moléculaire du C.N.R.S., Marseille, France.
authors.forename: V
authors.initials: V
authors.lastname: Geli
authors.forename: D
authors.initials: D
authors.lastname: Baty
authors.forename: F
authors.initials: F
authors.lastname: Pattus
authors.forename: C
authors.initials: C
authors.lastname: Lazdunski
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D003001:Cloning, Molecular; D003087:Colicins / Q000037:antagonists & inhibitors*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D008565:Membrane Proteins / Q000235:genetics*; D008961:Models, Structural; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; C488854:Cbi protein, E coli; D003087:Colicins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C007104:colicin immunity proteins; D000469:Alkaline Phosphatase