Abstract
The entire coding sequence of the tonB gene, except for nine codons at the 3′ end, was deleted from the chromosome of Escherichia coli. Introduction of the btuB451 suppressor mutant tonB1 into the chromosome of such a tonB deletion strain showed that the tonB1 allele was active as a suppressor in a single copy at 37° C and 42° C but not at 28° C. No temperature dependence was seen when FepA- or FhuA-dependent activities of the tonB1 gene product (TonBQ160K) were tested. The btuB451 suppressor activity of tonB1 was inhibited by the simultaneous presence within the cells of the tonB + allele on a multicopy plasmid. This represents the first case of dominance among different tonB alleles. Inhibition of suppression was abolished by overexpression of the btuB451-encoded receptor protein. Competition for binding of TonB+ and TonBQ150K to ExbB was excluded as the cause of dominance. Based on our data we conclude that competition for binding of TonB + and TonBQ160K to the btuB451 gene product is the reason for the observed dominance. The implications of these findings for the mechanism of btuB451 suppression by tonB1 are discussed.
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Anton M, Heller KJ (1991) Functional analysis of a C-terminally deleted TonB protein of Escherichia coli. Gene 105:23–29
Bell PE, Nau CD, Brown JT, Konisky J, Kadner RJ (1990) Genetic suppression demonstrates interaction of TonB protein with outer membrane transport proteins in Escherichia coli. J Bacteriol 172:3826–3829
Braun V (1989) The structurally related exbB and tolQ genes are interchangable in conferring tonB-dependent colicin, bacteriophage, and albomycin sensitivity. J Bacteriol 171:6387–6390
Braun V Günter K, Hantke K (1991) Transport of iron across the outer membrane. BioMetals 4:14–22
Brewer S, Tolley M, Trayer IP, Barr GC, Dorman CJ, Hannavy K, Higgins CF, Evans JS, Levine BA, Wormald MA (1990) Structure and function of X-Pro dipeptide repeats in the TonB proteins of Salmonella typhimurium and Escherichia coli. J Mot Biol 216:883–895
Eick-Helmerich K, Braun V (1989) Import of biopolymers into Escherichia coli: nucleotide sequences of the exbB and exbD genes are homologous to those of the tolQ and tolR genes, respectively. J Bacteriol 171:5117–5126
Fischer E, Günter K, Braun V (1989) Involvement of ExbB and TonB in transport across the outer membrane of Escherichia coli: phenotypic complementation of exbB mutants by overexpressed tonB and physical stabilization of TonB by ExbB. J Bacteriol 171:5127–5134
Gudmundsdottir A, Bell PE, Lundrigan MA, Kadner RJ (1989) Point mutations in a conserved region (TonB box) of the Escherichia coli outer membrane BtuB protein affect vitamin B12 transport. J Bacteriol 171:6526–6533
Günter K, Braun V (1990) In vivo evidence for FhuA outer membrane receptor interaction with the TonB inner membrane protein of Escherichia coli. FEBS Lett 274:85–88
Hamilton CM, Aldea M, Washburn BK, Babitzke P, Kushner SR (1989) New method for generating deletions and gene replacements in Escherichia coli. J Bacteriol 171:4617–4622
Hannavy K, Barr GC, Dorman CJ, Adamson J, Mazengera LR, Gallagher MP, Evans JS, Levine BA, Trayer IP, Higgins CF (1990) TonB of Salmonella typhimurium, a model for signal transduction between membranes. J Mot Biol 216:895–908
Heller KJ, Kadner RJ (1985) Nucleotide sequence of the gene for the vitamin B12 receptor protein in the outer membrane of Escherichia coli. J Bacteriol 161:904–908
Heller KJ, Mann BJ, Kadner RJ (1985) Cloning and expression of the gene for the vitamin B12 receptor protein in the outer membrane of Escherichia coli. J Bacteriol 161:896–893
Heller KJ, Kadner RJ, Günter K (1988) Suppression of the btuB451 mutation by mutations in the tonB gene suggests a direct interaction between TonB and TonB-dependent receptor proteins in the outer membrane of Escherichia coli. Gene 64:147–153
Kadner RJ (1990) Vitamin B12 transport in Escherichia coli: energy coupling between membranes. Mol Microbiol 4:2027–2033
Laemmli UK (1970) Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227:680–685
Mann BJ, Holroyd CD, Bradbeer C, Kadner RJ (1986) Reduced activity of TonB-dependent functions in strains of Escherichia coli. FEMS Microbiol Lett 33:255–260
Postle K (1990) TonB and the Gram-negative dilemma. Mol Microbiol 4:2019–2025
Postle K, Good RF (1983) DNA sequence of the Escherichia coli tonB gene. Proc Natl Acad Sci USA 80:5235–5239
Postle K, Skare JT (1988) Escherichia coli TonB protein is exported from the cytoplasm without proteolytic cleavage of its amino terminus. J Biol Chem 263:11000–11007
Prentki P, Krisch HM (1984) In vitro insertional mutagenesis with a selectable DNA fragment. Gene 29:303–313
Roof SK, Allard JD, Bertrand KP, Pestle K (1991) Analysis of Escherichia coli TonB membrane topology by use of PhoA fusions. J Bacteriol 173:5554–5557
Sambrook J, Fritsch EF, Maniatis T (1989) Molecular cloning: A laboratory manual, 2nd edn. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York
Schöffler H, Braun V (1989) Transport across the outer membrane of Escherichia coli K 12 via the FhuA receptor is regulated by the TonB protein of the cytoplasmic membrane. Mol Gen Genet 217:378–383
Silhavy TJ, Berman ML, Enquist LW (1984) Experiments with gene fusions. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York
Skare JT, Postle K (1991) Evidence for a TonB-dependent energy transduction complex in Escherichia coli. Mol Microbiol 5:2883–2890
Tabor S, Richardson CC (1985) A bacteriophage T7 RNA polymerase/promoter system for controlled exclusive expression of specific genes. Proc Natl Acad Sci USA 82:1074–1078
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Anton, M., Heller, K.J. The wild-type allele of tonB in Escherichia coli is dominant over the tonB1 allele, encoding TonBQ160K, which suppresses the btuB451 mutation. Molec. Gen. Genet. 239, 371–377 (1993). https://doi.org/10.1007/BF00276935
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DOI: https://doi.org/10.1007/BF00276935