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Free keywords:
Amino Acid Sequence; Bacillus/ch [Chemistry]; Bacillus/ul [Ultrastructure]; *Bacteria/ch [Chemistry]; *Bacterial Outer Membrane Proteins/ch [Chemistry]; Bacterial Outer Membrane Proteins/ul [Ultrastructure]; *Cell Membrane/ch [Chemistry]; Cell Membrane/ul [Ultrastructure]; Clostridium/ch [Chemistry]; Clostridium/ul [Ultrastructure]; Comparative Study; Crystallography; Macromolecular Systems; Molecular Sequence Data; Open Reading Frames; *Protein Structure, Secondary; Sequence Homology, Amino Acid; Support, Non-U.S. Gov't; Thermus thermophilus/ch [Chemistry]; Thermus thermophilus/ul [Ultrastructure]
Abstract:
The three-dimensional structure of the Acetogenium kivui surface layer (S-layer) has been determined to a resolution of 1.7 nm by electron crystallographic techniques. Two independent reconstructions were made from layers negatively stained with uranyl acetate and Na-phosphotungstate. The S-layer has p6 symmetry with a center-to-center spacing of approximately 19 nm. Within the layer, six monomers combine to form a ring-shaped core surrounded by a fenestrated rim and six spokes that point towards the axis of threefold symmetry and provide lateral connectivity to other hexamers in the layer. The structure of the A. kivui S-layer protein is very similar to that of the Bacillus brevis middle wall protein, with which it shares an N-terminal domain of homology. This domain is found in several other extracellular proteins, including the S-layer proteins from Bacillus sphaericus and Thermus thermophilus, Omp alpha from Thermotoga maritima, an alkaline cellulase from Bacillus strain KSM-635, and xylanases from Clostridium thermocellum and Thermoanaerobacter saccharolyticum, and may serve to anchor these proteins to the peptidoglycan. To our knowledge, this is the first example of a domain conserved in several S-layer proteins.
