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Characterization of a membrane-bound C-glucosyltransferase responsible for carminic acid biosynthesis in Dactylopius coccus Costa

2017; Nature Portfolio; Volume: 8; Issue: 1 Linguagem: Inglês

10.1038/s41467-017-02031-z

2041-1723

Rubini Kannangara, Lina Šiukštaitė, Jonas Borch-Jensen, Bjørn Stæhr Madsen, Kenneth T. Kongstad, Dan Stærk, Mads Bennedsen, Finn T. Okkels, Silas Anselm Rasmussen, Thomas O. Larsen, Rasmus John Normand Frandsen, Birger Lindberg Møller,

Insect symbiosis and bacterial influences

Abstract Carminic acid, a glucosylated anthraquinone found in scale insects like Dactylopius coccus , has since ancient times been used as a red colorant in various applications. Here we show that a membrane-bound C-glucosyltransferase, isolated from D . coccus and designated DcUGT2, catalyzes the glucosylation of flavokermesic acid and kermesic acid into their respective C-glucosides dcII and carminic acid. DcUGT2 is predicted to be a type I integral endoplasmic reticulum (ER) membrane protein, containing a cleavable N-terminal signal peptide and a C-terminal transmembrane helix that anchors the protein to the ER, followed by a short cytoplasmic tail. DcUGT2 is found to be heavily glycosylated. Truncated DcUGT2 proteins synthesized in yeast indicate the presence of an internal ER-targeting signal. The cleavable N-terminal signal peptide is shown to be essential for the activity of DcUGT2, whereas the transmembrane helix/cytoplasmic domains, although important, are not crucial for its catalytic function.