The tonB gene of Serratia marcescens: sequence, activity and partial complementation of Escherichia coli tonB mutants
| Autor: | Volkmar Braun, S. Gaisser |
|---|---|
| Rok vydání: | 1991 |
| Předmět: |
Molecular Sequence Data
Mutant Siderophores Iron Chelating Agents medicine.disease_cause Microbiology Bacterial Proteins Species Specificity Escherichia coli polycyclic compounds medicine Amino Acid Sequence Molecular Biology Peptide sequence Serratia marcescens chemistry.chemical_classification Base Sequence biology Escherichia coli Proteins Genetic Complementation Test Nucleic acid sequence Membrane Proteins biochemical phenomena metabolism and nutrition biology.organism_classification Amino acid chemistry Biochemistry Genes Bacterial Protein Biosynthesis Colicin bacteria Transformation Bacterial Bacterial outer membrane |
| Zdroj: | Molecular Microbiology. 5:2777-2787 |
| ISSN: | 1365-2958 0950-382X |
| Popis: | Summary The TonB protein plays a key role in the energy-coupled transport of iron siderophores, of vitamin B12, and of colicins of the B-group across the outer membrane of Escherichia coli. In order to obtain more data about which of its particular amino acid sequences are necessary for TonB function, we have cloned and sequenced the tonB gene of Serratia marcescens. The nucleotide sequence predicts an amino acid sequence of 247 residues (Mr 27389), which is unusually proline-rich and contains the tandem sequences (Glu-Pro)5 and (Lys-Pro)5. In contrast to the TonB proteins of E. coli and Salmonella typhimurium, translation of the S. marcescens TonB protein starts at the first methionine residue of the open reading frame, which is the only amino acid removed during TonB maturation and export. Only the N-terminal sequence is hydrophobic, suggesting its involvement in anchoring the TonB protein to the cytoplasmic membrane. The S. marcescens tonB gene complemented an E. coli tonB mutant with regard to uptake of iron siderophores, and sensitivity to phages T1 and φ 80, and to colicins B and M. However, an E. coli tonB mutant transformed with the S. marcescens tonB gene remained resistant to colicins la and Ib, to colicin B derivatives carrying the amino acid replacements Val/Ala and Val/Gly at position 20 in the TonB box, and they exhibited a tenfold lower activity with colicin D. In addition, the S. marcescens TonB protein did not restore T1 sensitivity of an E. coli exbB tolQ double mutant, as has been found for the overexpressed E. coli TonB protein, indicating a lower activity of the S. marcescens TonB protein. Although the S. marcescens TonB protein was less prone to proteolytic degradation, it was stabilized in E. coli by the ExbBD proteins. In E. coli, TonB activity of S. marcescens depended either on the ExbBD or the TolQR activities. |
| Databáze: | OpenAIRE |
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