Glycosylation is the most complex and widespread process of posttranslational modification of proteins and lipids, with an unsurpassed capacity to generate a wide array of structures.  The large polypeptide GalNAc-transferase (GalNAc-Ts) family catalyzes the transfer of N-acetylgalactosamine (GalNAc) from a sugar donor UDP-GalNAc to Ser/Thr side chains of cell-surface proteins . Deficiencies and dysregulation of individual GalNAc-Ts have been found to cause diseases and predispositions. Uncontrolled GalNAc-Ts expression alters mucin O-glycosylation influencing a variety of cancer-related functions . Therefore, is vitally needed to understand GalNAc-Ts binding specificities and their mechanism of action in health to further develop inhibitors in diseases such as cancer.
In this communication it will be reported the application of NMR methods to follow the mucin O-glycosylation by GalNAc-Ts by using a mucin structure with multiple tandem repeated domains, unveiling new structural, conformational and dynamic insights at atomic level of this biological event. Additionally, it was demonstrated that a GALNT2 mutant (F104S) leading to the inactivation of the enzyme, induces low levels of highdensity lipoprotein cholesterol (HDL-C) in humans. Thus, in this communication it will be also described the molecular basis behind the GalNAc-T2 F104S mutant inactivation, unraveled by the integrative application of X-ray diffraction analysis, molecular modeling and NMR spectroscopic techniques, namely STD-NMR and 19F-NMR .
Helena Coelho thanks the FCT-Portugal for the Projects IF/00780/2015, PTDC/BIA-MIB/31028/2017 and UID/Multi/04378/2019 and to the European commission for the project TOLLerant H2020-MSCETN-642157. The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No 22161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC).
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