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| {{STRUCTURE_1mn0| PDB=1mn0 | SCENE= }} | | {{STRUCTURE_1mn0| PDB=1mn0 | SCENE= }} |
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| '''Crystal structure of galactose mutarotase from lactococcus lactis complexed with D-xylose'''
| | ===Crystal structure of galactose mutarotase from lactococcus lactis complexed with D-xylose=== |
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| ==Overview==
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| Galactose 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_12218067}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 12218067 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_12218067}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Galactosemia]] | | [[Category: Galactosemia]] |
| [[Category: Sugar binding]] | | [[Category: Sugar binding]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 01:26:23 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Jul 3 00:25:13 2008'' |
