Omp85(Tt) from Thermus thermophilus HB27: an ancestral type of the Omp85 protein family.
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.
Nesper
Jutta
J
Department of Biology, University of Konstanz, 78457 Konstanz, Germany. Jutta.Nesper@uni-konstanz.de
Brosig
Alexander
A
Ringler
Philippe
P
Patel
Geetika J
GJ
Müller
Shirley A
SA
Kleinschmidt
Jörg H
JH
Boos
Winfried
W
Diederichs
Kay
K
Welte
Wolfram
W
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016963:Thermus thermophilus / Q000378:metabolism* / Q000648:ultrastructure
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D008565:Membrane Proteins