The MUR1 gene of Arabidopsis thaliana encodes an isoform of GDP-D-mannose-4,6-dehydratase, catalyzing the first step in the de novo synthesis of GDP-L-fucose.
GDP-L-fucose is the activated nucleotide sugar form of L-fucose, which is a constituent of many structural polysaccharides and glycoproteins in various organisms. The de novo synthesis of GDP-L-fucose from GDP-D-mannose encompasses three catalytic steps, a 4,6-dehydration, a 3,5-epimerization, and a 4-reduction. The mur1 mutant of Arabidopsis is deficient in L-fucose in the shoot and is rescued by growth in the presence of exogenously supplied L-fucose. Biochemical assays of the de novo pathway for the synthesis of GDP-L-fucose indicated that mur1 was blocked in the first nucleotide sugar interconversion step, a GDP-D-mannose-4,6-dehydratase. An expressed sequence tag was identified that showed significant sequence similarity to proposed bacterial GDP-D-mannose-4,6-dehydratases and was tightly linked to the mur1 locus. A full-length clone was isolated from a cDNA library, and its coding region was expressed in Escherichia coli. The recombinant protein exhibited GDP-D-mannose-4,6-dehydratase activity in vitro and was able to complement mur1 extracts in vitro to complete the pathway for the synthesis of GDP-L-fucose. All seven mur1 alleles investigated showed single point mutations in the coding region for the 4,6-dehydratase, confirming that it represents the MUR1 gene.
Bonin
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CP
Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269, USA.
Potter
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I
Vanzin
G F
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Reiter
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WD
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D015139:Blotting, Southern; D002238:Carbohydrate Epimerases / Q000378:metabolism; D002855:Chromatography, Thin Layer; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D015870:Gene Expression / Q000235:genetics; D017343:Genes, Plant; D006154:Guanosine Diphosphate Fucose / Q000096:biosynthesis*; D006836:Hydro-Lyases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007658:Ketone Oxidoreductases; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009097:Multienzyme Complexes; D009154:Mutation / Q000235:genetics; D016415:Sequence Alignment; D013401:Sugar Alcohol Dehydrogenases / Q000378:metabolism
D018076:DNA, Complementary; D029968:Escherichia coli Proteins; D007527:Isoenzymes; D009097:Multienzyme Complexes; C110682:wcaG protein, E coli; D006154:Guanosine Diphosphate Fucose; D013401:Sugar Alcohol Dehydrogenases; D007658:Ketone Oxidoreductases; D006836:Hydro-Lyases; C044971:GDPmannose 4,6-dehydratase; D002238:Carbohydrate Epimerases