-Arabinose in Plants: Molecular Cloning and Characterization of a Golgi-Localized UDP-
نویسندگان
چکیده
The mur4 mutant of Arabidopsis shows a 50% reduction in the monosaccharide L -Ara in leaf-derived cell wall material because of a partial defect in the 4-epimerization of UDPD -Xyl to UDPL -Ara. To determine the genetic lesion underlying the mur4 phenotype, the MUR4 gene was cloned by a map-based procedure and found to encode a type-II membrane protein with sequence similarity to UDPD -Glc 4-epimerases. Enzyme assays of MUR4 protein expressed in the methylotropic yeast Pichia pastoris indicate that it catalyzes the 4-epimerization of UDPD -Xyl to UDPL -Ara, the nucleotide sugar used by glycosyltransferases in the arabinosylation of cell wall polysaccharides and wall-resident proteoglycans. Expression of MUR4–green fluorescent protein constructs in Arabidopsis revealed localization patterns consistent with targeting to the Golgi, suggesting that the MUR4 protein colocalizes with glycosyltransferases in the biosynthesis of arabinosylated cell wall components. The Arabidopsis genome encodes three putative proteins with 76% sequence identity to MUR4, which may explain why mur4 plants are not entirely deficient in the de novo synthesis of UDPL -Ara.
منابع مشابه
Bifunctional cytosolic UDP-glucose 4-epimerases catalyse the interconversion between UDP-D-xylose and UDP-L-arabinose in plants.
UDP-sugars serve as substrates in the synthesis of cell wall polysaccharides and are themselves generated through sequential interconversion reactions from UDP-Glc (UDP-glucose) as the starting substrate in the cytosol and the Golgi apparatus. For the present study, a soluble enzyme with UDP-Xyl (UDP-xylose) 4-epimerase activity was purified approx. 300-fold from pea (Pisum sativum L.) sprouts ...
متن کاملThe biosynthesis of D-Galacturonate in plants. functional cloning and characterization of a membrane-anchored UDP-D-Glucuronate 4-epimerase from Arabidopsis.
Pectic cell wall polysaccharides owe their high negative charge to the presence of D-galacturonate, a monosaccharide that appears to be present only in plants and some prokaryotes. UDP-D-galacturonate, the activated form of this sugar, is known to be formed by the 4-epimerization of UDP-D-glucuronate; however, no coding regions for the epimerase catalyzing this reaction have previously been des...
متن کاملMolecular Cloning, Characterization, and Expression of Cuc m 2, a Major Allergen in Cucumis melo
Background: Several studies reported the clinical features of IgE-mediated hypersensitivity after ingestion of melon. Melon allergy is a common IgE-mediated fruit allergy in Iran. This prompted us to investigate immunochemical and molecular properties of the major allergen in melon fruit, to compare the IgE-binding capacity of the natural protein with the recombinant allergen, and to determine ...
متن کاملDetection, Cloning, Molecular Characterization and Phylogenic Analyses of a New Primate T-Cell Lymphotropic Virus Type I in Olive Baboon
متن کامل
UDP-sugar pyrophosphorylase is essential for arabinose and xylose recycling, and is required during vegetative and reproductive growth in Arabidopsis
Numerous nucleotide sugars are needed in plants to synthesize cell wall polymers and glycoproteins. The de novo synthesis of nucleotide sugars is of major importance. During growth, however, some polymers are broken down to monosaccharides. Reactivation of these sugars into nucleotide sugars occurs in two steps: first, by a substrate-specific sugar-1-kinase and, second, by UDP-sugar-pyrophospho...
متن کامل