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.
Kim
Min-Sung
MS
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.
Shin
Joon
J
Lee
Weontae
W
Lee
Heung-Soo
HS
Oh
Byung-Ha
BH
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