Voltage sensing in the PhoE and OmpF outer membrane porins of Escherichia coli: role of charged residues
| Autor: | Ria van Boxtel, Jurg P. Rosenbusch, Prashant S. Phale, Alexej Prilipov, Elaine F Eppens, Jan Tommassen, Patrick Van Gelder, Nathalie Saint |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
Cell Membrane Permeability
Chemistry Escherichia coli Proteins Conductance Porins Gating Permeation medicine.disease_cause Electrophysiology Residue (chemistry) chemistry.chemical_compound Monomer Biochemistry Structural Biology Mutagenesis Porin Biophysics medicine Escherichia coli Bacterial outer membrane Molecular Biology Ion Channel Gating Bacterial Outer Membrane Proteins |
| Zdroj: | Journal of molecular biology. 269(4) |
| ISSN: | 0022-2836 |
| Popis: | The porins PhoE and OmpF form anion and cation-selective pores, respectively, in the outer membrane of Escherichia coli. Each monomer of these trimeric proteins consists of a 16-stranded beta-barrel, which contains a constriction at half the height of the channel. The functional significance of a transverse electrical field that is formed by charged amino acid residues within the constriction zone was investigated. For this purpose, the PhoE residues R37, R75, K18 and E110 were substituted by neutral amino acids. The mutant pores allowed an increased permeation of beta-lactam antibiotics across the outer membrane in vivo, although the single channel conductance, measured in planar lipid bilayers, was not increased or even slightly decreased. Replacement of the positively charged residues resulted in a decreased voltage sensitivity, whereas the substitution of a negatively charged residue resulted in an increased voltage sensitivity. Similar substitutions in OmpF caused the opposite effects, i.e. the substitution of positive and negative charges resulted in increased and decreased voltage sensitivity, respectively. Together, the results suggest that opposite charges, i.e. positive charges in anion-selective and negative charges in cation-selective porins, act as sensors for voltage gating. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect