Journal article
Omp85(Tt) from Thermus thermophilus HB27: an ancestral type of the Omp85 protein family
Publication Details
Authors: | Nesper, J.; Brosig, A.; Ringler, P.; Patel, G.; Müller, S.; Kleinschmidt, J.; Boos, W.; Diederichs, K.; Welte, W. |
Publisher: | American Society for Microbiology |
Publication year: | 2008 |
Journal: | Journal of Bacteriology |
Pages range : | 4568-4575 |
Volume number: | 190 |
ISSN: | 0021-9193 |
eISSN: | 1098-5530 |
DOI-Link der Erstveröffentlichung: |
Abstract
Proteins belonging to the Omp85 family are involved in the assembly of beta-barrel outer membrane proteins or in the translocation of proteins across the outer membrane in bacteria, mitochondria, and chloroplasts. The cell envelope of the thermophilic bacterium Thermus thermophilus HB27 is multilayered, including an outer membrane that is not well characterized. Neither the precise lipid composition nor much about integral membrane proteins is known. The genome of HB27 encodes one Omp85-like protein, Omp85(Tt), representing an ancestral type of this family. We overexpressed Omp85(Tt) in T. thermophilus and purified it from the native outer membranes. In the presence of detergent, purified Omp85(Tt) existed mainly as a monomer, composed of two stable protease-resistant modules. Circular dichroism spectroscopy indicated predominantly beta-sheet secondary structure. Electron microscopy of negatively stained lipid-embedded Omp85(Tt) revealed ring-like structures with a central cavity of approximately 1.5 nm in diameter. Single-channel conductance recordings indicated that Omp85(Tt) forms ion channels with two different conducting states, characterized by conductances of approximately 0.4 nS and approximately 0.65 nS, respectively.
Proteins belonging to the Omp85 family are involved in the assembly of beta-barrel outer membrane proteins or in the translocation of proteins across the outer membrane in bacteria, mitochondria, and chloroplasts. The cell envelope of the thermophilic bacterium Thermus thermophilus HB27 is multilayered, including an outer membrane that is not well characterized. Neither the precise lipid composition nor much about integral membrane proteins is known. The genome of HB27 encodes one Omp85-like protein, Omp85(Tt), representing an ancestral type of this family. We overexpressed Omp85(Tt) in T. thermophilus and purified it from the native outer membranes. In the presence of detergent, purified Omp85(Tt) existed mainly as a monomer, composed of two stable protease-resistant modules. Circular dichroism spectroscopy indicated predominantly beta-sheet secondary structure. Electron microscopy of negatively stained lipid-embedded Omp85(Tt) revealed ring-like structures with a central cavity of approximately 1.5 nm in diameter. Single-channel conductance recordings indicated that Omp85(Tt) forms ion channels with two different conducting states, characterized by conductances of approximately 0.4 nS and approximately 0.65 nS, respectively.
Keywords
Bacterial Outer Membrane Proteins, Bacterial Outer Membrane Proteins/chemistry/genetics/metabolism, Bacterial Proteins, Bacterial Proteins/chemistry/genetics/metabolism, Circular Dichroism, Lipid Bilayers, Lipid Bilayers, Lipid Bilayers/chemistry/metabolism, Membrane Lipids, Membrane Lipids/chemistry/metabolism, Membrane Proteins, Membrane Proteins/chemistry/genetics/metabolism, Thermus thermophilus/metabolism/ultrastructure
