Crystal Structure of a Major Outer Membrane Protein from Thermus thermophilus HB27

The thermophilic eubacterium Thermus thermophilus belongs to one of the oldest branches of evolution and has a multilayered cell envelope that differs from that of modern Gram-negative bacteria. Its outer membrane contains integral outer membrane proteins (OMPs), of which only a few are characterize...

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Bibliographic Details
Published in:Journal of molecular biology 2009-02, Vol.385 (5), p.1445-1455
Main Authors: Brosig, Alexander, Nesper, Jutta, Boos, Winfried, Welte, Wolfram, Diederichs, Kay
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacterial Outer Membrane Proteins - chemistry
Cations, Divalent - chemistry
Crystallography, X-Ray
Eubacterium
Models, Molecular
Molecular Sequence Data
outer membrane biogenesis
Protein Structure, Secondary
T. thermophilus
thermophile
Thermus
Thermus thermophilus
Thermus thermophilus - chemistry
TTC0834
TTC1475
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Summary:The thermophilic eubacterium Thermus thermophilus belongs to one of the oldest branches of evolution and has a multilayered cell envelope that differs from that of modern Gram-negative bacteria. Its outer membrane contains integral outer membrane proteins (OMPs), of which only a few are characterized. TtoA, a new β-barrel OMP, was identified by searching the genome sequence of strain HB27 for the presence of a C-terminal signature sequence. The structure of TtoA was determined to a resolution of 2.8 Å, representing the first crystal structure of an OMP from a thermophilic bacterium. TtoA consists of an eight-stranded β-barrel with a large extracellular part to which a divalent cation is bound. A five-stranded extracellular β-sheet protrudes out of the membrane-embedded transmembrane barrel and is stabilized by a disulfide bridge. The edge of this β-sheet forms crystal contacts that could mimic interactions with other proteins. In modern Gram-negative bacteria, the C-terminal signature sequence of OMPs is required for binding to an Omp85 family protein as a prerequisite for its assembly. We present hints that a similar assembly pathway exists in T. thermophilus by an in vitro binding assay, where unfolded TtoA binds to the Thermus Omp85 family protein TtOmp85, while a mutant without the signature sequence does not.
ISSN:0022-2836
1089-8638
DOI:10.1016/j.jmb.2008.12.003