title: A ColE1-encoded gene directs entry exclusion of the plasmid.
abstract: To detect entry exclusion of the ColE1 plasmid, we established an assay system that was not influenced by incompatibility of extant plasmids in the recipient cells or by the viability of the cells due to the killing action of colicin E1 protein. The assay revealed that exc1 and exc2, assigned as genes directing entry exclusion, had no exclusion activity. Instead, mbeD, which had been characterized as a gene for plasmid mobilization, directed the exclusion activity. MbeD was overexpressed and identified as a 35S-labeled protein, which was recovered in both the soluble and membrane fractions, particularly in the inner membrane fraction. An amphipathic helical structure was predicted in the N-terminal region of MbeD as well as in the corresponding homologous proteins of ColA and ColK. These proteins may bind to the inner membrane via the N-terminal amphipathic helix and function in entry exclusion.
authors.affiliation: Department of Biochemistry, Yamaguchi University School of Medicine, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamada
authors.forename: M
authors.initials: M
authors.lastname: Yamada
authors.forename: A
authors.initials: A
authors.lastname: Nakazawa
mesh_terms: D000595:Amino Acid Sequence; D002451:Cell Compartmentation; D003001:Cloning, Molecular; D003087:Colicins / Q000737:chemistry / Q000235:genetics*; D003227:Conjugation, Genetic; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D017433:Protein Structure, Secondary; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid
chemical_list: D003087:Colicins