1e6u | pdb_00001e6u
GDP 4-KETO-6-DEOXY-D-MANNOSE EPIMERASE REDUCTASE
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 PubMedGDP-4-keto-6-deoxy-d-mannose epimerase/reductase is a bifunctional enzyme responsible for the last step in the biosynthesis of GDP-l-fucose, the substrate of fucosyl transferases. Several cell-surface antigens, including the leukocyte Lewis system and cell-surface antigens in pathogenic bacteria, depend on the availability of GDP-l-fucose for their expression. Therefore, the enzyme is a potential target for therapy in pathological states depending on selectin-mediated cell-to-cell interactions. Previous crystallographic investigations have shown that GDP-4-keto-6-deoxy-d-mannose epimerase/reductase belongs to the short-chain dehydrogenase/reductase protein homology family. The enzyme active-site region is at the interface of an N-terminal NADPH-binding domain and a C-terminal domain, held to bind the substrate. The design, expression and functional characterization of seven site-specific mutant forms of GDP-4-keto-6-deoxy-d-mannose epimerase/reductase are reported here. In parallel, the crystal structures of the native holoenzyme and of three mutants (Ser107Ala, Tyr136Glu and Lys140Arg) have been investigated and refined at 1. 45-1.60 A resolution, based on synchrotron data (R-factors range between 12.6 % and 13.9 %). The refined protein models show that besides the active-site residues Ser107, Tyr136 and Lys140, whose mutations impair the overall enzymatic activity and may affect the coenzyme binding mode, side-chains capable of proton exchange, located around the expected substrate (GDP-4-keto-6-deoxy-d-mannose) binding pocket, are selectively required during the epimerization and reduction steps. Among these, Cys109 and His179 may play a primary role in proton exchange between the enzyme and the epimerization catalytic intermediates. Finally, the additional role of mutated active-site residues involved in substrate recognition and in enzyme stability has been analyzed. Probing the catalytic mechanism of GDP-4-keto-6-deoxy-d-mannose Epimerase/Reductase by kinetic and crystallographic characterization of site-specific mutants.,Rosano C, Bisso A, Izzo G, Tonetti M, Sturla L, De Flora A, Bolognesi M J Mol Biol. 2000 Oct 13;303(1):77-91. PMID:11021971[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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