1mn0 | pdb_00001mn0
Crystal structure of galactose mutarotase from lactococcus lactis complexed with D-xylose
Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedGalactose mutarotase catalyzes the conversion of beta-D-galactose to alpha-D-galactose in the Leloir pathway for galactose metabolism. The high resolution x-ray structure of the dimeric enzyme from Lactococcus lactis was recently solved and shown to be topologically similar to the 18-stranded, anti-parallel beta-motif observed for domain 5 of beta-galactosidase. In addition to determining the overall molecular fold of galactose mutarotase, this initial investigation also provided a detailed description of the electrostatic interactions between the enzyme and its physiologically relevant substrate, galactose. Specifically, the side chains of His-96 and His-170 were shown to be located within hydrogen bonding distance to the C-5 oxygen of the substrate, while the carboxylate of Glu-304 was positioned near the C-1 hydroxyl group of the sugar. On the basis of this initial study, a possible role for Glu-304 as the general acid/base group in catalysis was put forth. Here we describe the combined x-ray crystallographic and kinetic analyses of L. lactis galactose mutarotase complexed with D-glucose, D-fucose, D-quinovose, L-arabinose, or D-xylose. These investigations have revealed that there are several distinct binding modes for these sugars, which are dependent upon the spatial orientation of the C-4 hydroxyl group. In those sugars with the same C-4 hydroxyl group orientation as galactose, their C-1 hydroxyl groups are invariably located near Glu-304. For those sugars, which have the same C-4 hydroxyl group configuration as glucose, the C-1 hydroxyls are typically located near Asp-243. These different binding modes correlate with both the observed kinetic parameters and the presence or absence of a hydrogen bond between the guanidinium group of Arg-71 and the C-4 hydroxyl group of the sugar ligand. Structural and kinetic studies of sugar binding to galactose mutarotase from Lactococcus lactis.,Thoden JB, Kim J, Raushel FM, Holden HM J Biol Chem. 2002 Nov 22;277(47):45458-65. Epub 2002 Sep 5. PMID:12218067[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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