Crystal structures of RbsD leading to the identification of cytoplasmic sugar-binding proteins with a novel folding architecture.
RbsD is the only protein whose biochemical function is unknown among the six gene products of the rbs operon involved in the active transport of ribose. FucU, a paralogue of RbsD conserved from bacteria to human, is also the only protein whose function is unknown among the seven gene products of the l-fucose regulon. Here we report the crystal structures of Bacillus subtilis RbsD, which reveals a novel decameric toroidal assembly of the protein. Nuclear magnetic resonance and other studies on RbsD reveal that the intersubunit cleft of the protein binds specific forms of d-ribose, but it does not have an enzyme activity toward the sugar. Likewise, FucU binds l-fucose but lacks an enzyme activity toward this sugar. We conclude that RbsD and FucU are cytoplasmic sugar-binding proteins, a novel class of proteins whose functional role may lie in helping influx of the sugar substrates.
Center for Biomolecular Recognition and Division of Molecular and Life Science, Department of Life Science, Pohang University of Science and Technology, Pohang, Kyungbuk, 790-784, Korea.
Min-Sung
MS
Kim
Joon
J
Shin
Weontae
W
Lee
Heung-Soo
HS
Lee
Byung-Ha
BH
Oh
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000378:metabolism; D001665:Binding Sites; D002151:Calorimetry; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D005643:Fucose / Q000378:metabolism; D005990:Glycerol / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012266:Ribose / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
D009004:Monosaccharide Transport Proteins; D005643:Fucose; D012266:Ribose; D005990:Glycerol