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Structural and Mechanistic Insights into the Catalytic-Domain-Mediated Short-Range Glycosylation Preferences of GalNAc-T4
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Resumo(s)
Mucin-type O-glycosylation is initiated by a family of polypeptide GalNAc-transferases (GalNAc-Ts) which are type-II transmembrane proteins that contain Golgi luminal catalytic and lectin domains that are connected by a flexible linker. Several GalNAc-Ts, including GalNAc-T4, show both long-range and short-range prior glycosylation specificity, governed by their lectin and catalytic domains, respectively. While the mechanism of the lectin-domain-dependent glycosylation is well-known, the molecular basis for the catalytic-domain-dependent glycosylation of glycopeptides is unclear. Herein, we report the crystal structure of GalNAc-T4 bound to the diglycopeptide GAT GAGAGAGT TPGPG (containing two α-GalNAc glycosylated Thr (T ), the PXP motif and a "naked" Thr acceptor site) that describes its catalytic domain glycopeptide GalNAc binding site. Kinetic studies of wild-type and GalNAc binding site mutant enzymes show the lectin domain GalNAc binding activity dominates over the catalytic domain GalNAc binding activity and that these activities can be independently eliminated. Surprisingly, a flexible loop protruding from the lectin domain was found essential for the optimal activity of the catalytic domain. This work provides the first structural basis for the short-range glycosylation preferences of a GalNAc-T.
Descrição
info:eu-repo/grantAgreement/FCT/5876/147258/PT We thank synchrotron radiation sources DLS (Oxford) and in particular beamline I03 (experiment number MX10121-15). We thank ARAID, MEC (CTQ2013-44367-C2-2-P, BFU2016-75633-P, CTQ2015-67727-R, CTQ2015-70524-R, and CTQ2017-85496-P), AGAUR (SGR2017-1189), the National Institutes of Health (R01-GM113534, and instrument Grant GM113534-01S to T. A. Gerken), the Danish National Research Foundation (DNRF107), the FCT-Portugal [UID/Multi/04378/2013 cofinanced by the FEDER (POCI-01-0145-FEDER-007728)], and the DGA (E34_R17) for financial support. I. Comparion thanks Universidad de La Rioja for the FPI grant. F. Marcelo thanks FCT-Portugal for IF Investigator grant (IF/00780/2015) and PTNMR supported by Project 022161. E. Lira-Navarrete acknowledges her postdoctoral EMBO fellowship ALTF 1553-2015 cofunded by the European Commission (LTFCOFUND2013, GA-2013-609409) and Marie Curie Actions. H. Coelho and J. Jimenez-Barbero thank EU for the TOLLerant project. The research leading to these results has also received funding from the FP7 (2007-2013) under BioStruct-X (Grant agreement 283570 and BIOSTRUCTX 5186). We would also like to acknowledge the assistance of Juwan Lee in obtaining the GaINAc-T4 random peptide motifs.
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General Chemistry General Chemical Engineering