Methylation of selenocysteine catalysed by thiopurine S-methyltransferase

Urbančič, Dunja (author), Kotar, Anita (author), Šmid, Alenka (author), Jukič, Marko (author), Gobec, Stanislav (author), Martensson, Lars (author), Plavec, Janez (author), Mlinarič-Raščan, Irena (author)

Background: Methylation driven by thiopurine S-methylatransferase (TPMT) is crucial for deactivation of cytostatic and immunosuppressant thiopurines. Despite its remarkable integration into clinical practice, the endogenous function of TPMT is unknown. Methods: To address the role of TPMT in methylation of selenium compounds, we established the research on saturation transfer difference (STD) and 77Se NMR spectroscopy, fluorescence measurements, as well as computational molecular docking simulations. Results: Using STD NMR spectroscopy and fluorescence measurements of tryptophan residues in TPMT, we determined the binding of selenocysteine (Sec) to human recombinant TPMT. By comparing binding characteristics of Sec in the absence and in the presence of methyl donor, we confirmed S-adenosylmethionine (SAM)-induced conformational changes in TPMT. Molecular docking analysis positioned Sec into the active site of TPMT with orientation relevant for methylation reaction. Se-methylselenocysteine (MeSec), produced in the enzymatic reaction, was detected by 77Se NMR spectroscopy. A direct interaction between Sec and SAM in the active site of rTPMT and the formation of both products, MeSec and S-adenosylhomocysteine, was demonstrated using NMR spectroscopy. Conclusions: The present study provides evidence on in vitro methylation of Sec by rTPMT in a SAM-dependant manner. General significance: Our results suggest novel role of TPMT and demonstrate new insights into enzymatic modifications of the 21st amino acid.

• Language: English
• Keywords: binding analysis, enzymatic methylation, NMR spectroscopy, S-adenosylmethionine, selenocysteine, thiopurine S-methyltransferase
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FFA - Faculty of Pharmacy
• Publication status: Published
• Publication version: Version of Record
• Year: 2019
• Number of pages: Str. 182-190
• Numbering: Vol. 1863, iss. 1
• PID: 20.500.12556/RUL-125358
• UDC: 543.429.23:615
• ISSN on article: 0304-4165
• DOI: 10.1016/j.bbagen.2018.10.002
• COBISS.SI-ID: 4616561
• Publication date in RUL: 12.03.2021

Record is a part of a journal

• Title: Biochimica et biophysica acta (G). General subjects
• Shortened title: Biochim. biophys. acta (G)
• Publisher: Elsevier
• ISSN: 0304-4165
• COBISS.SI-ID: 20760839

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.
• Licensing start date: 12.03.2021

Secondary language

• Language: Slovenian
• Keywords: jedrska magnetna resonanca, analizne metode, S-metiltransferaze