Identification and characterization of abeta1,3-glucosyltransferase that synthesizes the Glc-beta1,3-Fuc disaccharide on thrombospondin type 1 repeats.
Thrombospondin type 1 repeats (TSRs) are biologically important domains of extracellular proteins. They are modified with a unique Glcbeta1,3Fucalpha1-O-linked disaccharide on either serine or threonine residues. Here we identify the putative glycosyltransferase, B3GTL, as the beta1,3-glucosyltransferase involved in the biosynthesis of this disaccharide. This enzyme is conserved from Caenorhabditis elegans to man and shares 28% sequence identity with Fringe, the beta1,3-N-acetylglucosaminyltransferase that modifies O-linked fucosyl residues in proteins containing epidermal growth factor-like domains, such as Notch. beta1,3-Glucosyltransferase glucosylates properly folded TSR-fucose but not fucosylated epidermal growth factor-like domain or the non-fucosylated modules. Specifically, the glucose is added in a beta1,3-linkage to the fucose in TSR. The activity profiles of beta1,3-glucosyltransferase and protein O-fucosyltransferase 2, the enzyme that carries out the first step in TSR O-fucosylation, superimpose in endoplasmic reticulum subfractions obtained by density gradient centrifugation. Both enzymes are soluble proteins that efficiently modify properly folded TSR modules. The identification of the beta1,3-glucosyltransferase gene allows us to manipulate the formation of the rare Glcbeta1,3Fucalpha1 structure to investigate its biological function.
Kozma
Krisztina
K
Friedrich Miescher Institute, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.
Keusch
Jeremy J
JJ
Hegemann
Björn
B
Luther
Kelvin B
KB
Klein
Dominique
D
Hess
Daniel
D
Haltiwanger
Robert S
RS
Hofsteenge
Jan
J
D000818:Animals; D017173:Caenorhabditis elegans; D002499:Centrifugation, Density Gradient; D004187:Disaccharides / Q000737:chemistry*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000737:chemistry; D005643:Fucose / Q000737:chemistry; D005964:Glucosyltransferases / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D010455:Peptides / Q000737:chemistry; D051381:Rats; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D019699:Thrombospondins / Q000737:chemistry*
D004187:Disaccharides; D010455:Peptides; D019699:Thrombospondins; D005643:Fucose; D004815:Epidermal Growth Factor; D005964:Glucosyltransferases; C120480:fucose 1,3-glucosyltransferase