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Structural insights into the N-terminal GIY–YIG endonuclease activity of Arabidopsis glutaredoxin AtGRXS16 in chloroplasts
- Liu, Xi, Liu, Shian, Feng, Yingang, Liu, Jian-Zhong, Chen, Yuling, Pham, Khanh, Deng, Haiteng, Hirschi, Kendal D., Wang, Xinquan, Cheng, Ninghui
- Proceedings of the National Academy of Sciences of the United States of America 2013 v.110 no.23 pp. 9565-9570
- Arabidopsis thaliana, DNA, DNA damage, chloroplasts, disulfide bonds, metabolism, mutation, oxidative stress, yeasts
- Glutaredoxins (Grxs) have been identified across taxa as important mediators in various physiological functions. A chloroplastic monothiol glutaredoxin, AtGRXS16 from Arabidopsis thaliana , comprises two distinct functional domains, an N-terminal domain (NTD) with GlyIleTyr-TyrIleGly (GIY-YIG) endonuclease motif and a C-terminal Grx module, to coordinate redox regulation and DNA cleavage in chloroplasts. Structural determination of AtGRXS16-NTD showed that it possesses a GIY–YIG endonuclease fold, but the critical residues for the nuclease activity are different from typical GIY–YIG endonucleases. AtGRXS16-NTD was able to cleave λDNA and chloroplast genomic DNA, and the nuclease activity was significantly reduced in AtGRXS16. Functional analysis indicated that AtGRXS16-NTD could inhibit the ability of AtGRXS16 to suppress the sensitivity of yeast grx5 cells to oxidative stress; however, the C-terminal Grx domain itself and AtGRXS16 with a Cys123Ser mutation were active in these cells and able to functionally complement a Grx5 deficiency in yeast. Furthermore, the two functional domains were shown to be negatively regulated through the formation of an intramolecular disulfide bond. These findings unravel a manner of regulation for Grxs and provide insights into the mechanistic link between redox regulation and DNA metabolism in chloroplasts.