Crystal structure and functional characterization of OmpK36, the osmoporin of Klebsiella pneumoniae
| Autor: | Sebastián Albertí, Santiago Hernández-Allés, Tilman Schirmer, Gabriele Rummel, Jurg P. Rosenbusch, Prashant S. Phale, V J Benedí, Raimund Dutzler |
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| Přispěvatelé: | University of Zurich, Schirmer, T |
| Rok vydání: | 1999 |
| Předmět: |
Models
Molecular Cell Membrane Permeability Protein Conformation Detergents Molecular Sequence Data Porins Biology Crystallography X-Ray outer membrane protein 1315 Structural Biology Bacterial Proteins Structural Biology Osmotic Pressure Sequence Homology Nucleic Acid 10019 Department of Biochemistry 1312 Molecular Biology Osmotic pressure Molecular replacement Lipid bilayer Molecular Biology nonspecific porin OmpK36 Alanine Osmotic concentration Base Sequence Biological Transport Gene Expression Regulation Bacterial biochemical phenomena metabolism and nutrition electrophysiology Klebsiella pneumoniae Biochemistry Membrane protein Porin Biophysics 570 Life sciences biology bacteria Carbohydrate Metabolism X-ray structure Bacterial outer membrane Sequence Alignment |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| ISSN: | 0969-2126 |
| Popis: | Background: Porins are channel-forming membrane proteins that confer solute permeability to the outer membrane of Gram-negative bacteria. In Escherichia coli, major nonspecific porins are matrix porin (OmpF) and osmoporin (OmpC), which show high sequence homology. In response to high osmolarity of the medium, OmpC is expressed at the expense of OmpF porin. Here, we study osmoporin of the pathogenic Klebsiella pneumoniae (OmpK36), which shares 87% sequence identity with E. coliOmpC in an attempt to establish why osmoporin is best suited to function at high osmotic pressure.Results: The crystal structure of OmpK36 has been determined to a resolution of 3.2 Å by molecular replacement with the model of OmpF. The structure of OmpK36 closely resembles that of the search model. The homotrimeric structure is composed of three hollow 16-stranded antiparallel β barrels, each delimiting a separate pore. Most insertions and deletions with respect to OmpF are found in the loops that protrude towards the cell exterior. A characteristic ten-residue insertion in loop 4 contributes to the subunit interface. At the pore constriction, the replacement of an alanine by a tyrosine residue does not alter the pore profile of OmpK36 in comparison with OmpF because of the different course of the mainchain. Functionally, as characterized in lipid bilayers and liposomes, OmpK36 resembles OmpC with decreased conductance and increased cation selectivity in comparison with OmpF.Conclusions: The osmoporin structure suggests that not an altered pore size but an increase in charge density is the basis for the distinct physico-chemical properties of this porin that are relevant for its preferential expression at high osmotic strength. The work was supported by grants from the Swiss National Science Foundation to JPR and TS, and from Ministerio de Educación y Cultura to VJB, SHA and SA were supported by a pre-doctoral fellowship and a post-doctoral contract, respectively, from Ministerio de Educación y Cultura. |
| Databáze: | OpenAIRE |
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