Skip to main content


Front. Plant Sci.
Sec. Plant Proteomics and Protein Structural Biology
Volume 15 - 2024 | doi: 10.3389/fpls.2024.1343066

E. coli expressed SECRET AGENT O-GlcNAc modifies threonine 829 of GIGANTEA

Provisionally accepted
  • 1 Department of Plant and Microbial Biology, University of Minnesota Twin Cities, St. Paul, Minnesota, United States
  • 2 University of Minnesota System, Saint Paul, Minnesota, United States

The final, formatted version of the article will be published soon.

    The Arabidopsis thaliana glycosyl transferases SPINDLY (SPY) and SECRET AGENT (SEC) modify nuclear and cytosolic protein with O-linked fucose or O-linked N-acetylglucosamine (O-GlcNAc), respectively. O-fucose and O-GlcNAc modifications can occur at the same sites. SPY interacts physically and genetically with GIGANTEA (GI) suggesting it may be modified by both enzymes. Previously, we found that when co-expressed in E. coli SEC modifies GI, however, the modification site was not determined. By analyzing overlapping sub-fragments of GI, we identified a region that was modified by SEC in E. coli. Modification was undetectable when threonine 829 (T829) was mutated to alanine while the T834A and T837A mutations reduced modification suggesting that T829 was the primary or only modification site. Mapping using mass spectrometry detected only modification of T829. Previous studies have shown that positions modified by SEC in E. coli are modified in planta suggesting that T829 is O-GlcNAc modified in planta.

    Keywords: GIGANTEA, O-GlcNAc, Secret Agent, posttranslational modification, Mass Spectrometry

    Received: 22 Nov 2023; Accepted: 12 Mar 2024.

    Copyright: © 2024 Kim, Hartweck and Olszewski. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Neil Olszewski, Department of Plant and Microbial Biology, University of Minnesota Twin Cities, St. Paul, 55108, Minnesota, United States

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.