{"entity": "publication", "iuid": "384831bd038048c29a66fa15d59e7325", "timestamp": "2026-04-13T05:35:06.295Z", "links": {"self": {"href": "https://publications.scilifelab.se/publication/384831bd038048c29a66fa15d59e7325.json"}, "display": {"href": "https://publications.scilifelab.se/publication/384831bd038048c29a66fa15d59e7325"}}, "title": "Details in the catalytic mechanism of mammalian thioredoxin reductase 1 revealed using point mutations and juglone-coupled enzyme activities.", "authors": [{"family": "Xu", "given": "Jianqiang", "initials": "J"}, {"family": "Cheng", "given": "Qing", "initials": "Q"}, {"family": "Arn\u00e9r", "given": "Elias S J", "initials": "ES"}], "type": "journal article", "published": "2016-05-00", "journal": {"volume": "94", "issn": "1873-4596", "issue": null, "pages": "110-120", "title": "Free Radic. Biol. Med.", "issn-l": "0891-5849"}, "abstract": "The mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a key enzyme in redox regulation, antioxidant defense, and cellular growth. TrxR1 can catalyze efficient reduction of juglone (5-hydroxy-1,4-naphthoquinone; walnut toxin) in a reaction which, in contrast to reduction of most other substrates of TrxR1, is not dependent upon an intact selenocysteine (Sec, U) residue of the enzyme. Using a number of TrxR1 mutant variants, we here found that a sole Cys residue at the C-terminal tail of TrxR1 is required for high-efficiency juglone-coupled NADPH oxidase activity of Sec-deficient enzyme, occurring with mixed one- and two-electron reactions producing superoxide. The activity also utilizes the FAD and the N-terminal redox active disulfide/dithiol motif of TrxR1. If a sole Cys residue at the C-terminal tail of TrxR1, in the absence of Sec, was moved further towards the C-terminal end of the protein compared to its natural position at residue 497, juglone reduction was, surprisingly, further increased. Ala substitutions of Trp407, Asn418 and Asn419 in a previously described \"guiding bar\", thought to mediate interactions of the C-terminal tail of TrxR1 with the FAD/dithiol site at the N-terminal domain of the other subunit in the dimeric enzyme, lowered turnover with juglone about 4.5-fold. Four residues of Sec-deficient TrxR1 were found to be easily arylated by juglone, including the Cys residue at position 497. Based upon our observations we suggest a model for involvement of the juglone-arylated C-terminal motif of TrxR1 to explain its high activity with juglone. This study thus provides novel insights into the catalytic mechanisms of TrxR1. One-electron juglone reduction by TrxR1 producing superoxide should furthermore contribute to the well-known prooxidant cytotoxicity of juglone.", "doi": "10.1016/j.freeradbiomed.2016.02.013", "pmid": "26898501", "labels": {"Mass Spectrometry-based Proteomics, Uppsala": "Service"}, "xrefs": [{"db": "pii", "key": "S0891-5849(16)00064-2"}], "notes": [], "created": "2017-05-03T13:02:34.764Z", "modified": "2017-06-12T11:40:05.356Z"}