期刊
PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS
卷 78, 期 14, 页码 3033-3047出版社
WILEY
DOI: 10.1002/prot.22827
关键词
GT-1; trihelix DNA-binding domain; transcription factor; phosphorylation; phosphomimetic mutant; NMR; solution structure
资金
- MEXT [21370047, 2057011, 22121517]
- Japan Science and Technology [04-183, SENTAN]
- Yokohama City University [K2102]
- Advanced Medical Research Center of Yokohama City University
- NIH [P41 RR-01081]
- Grants-in-Aid for Scientific Research [21370047, 22121517] Funding Source: KAKEN
GT-1 is a plant transcription factor that binds to one of the cis-acting elements, BoxII, which resides within the upstream promoter region of light-responsive genes. GT-1 was assumed to act as a molecular switch modulated through Ca2+-dependent phosphorylation/dephosphorylation in response to light signals. It was shown previously that the phosphorylation of threonine 133 in the DNA-binding domain (DBD) of GT-1 results in enhancement of the BoxII-binding activity. Interestingly, point mutation of Thr133 to Asp also enhances the BoxII-binding activity. Here, we report the solution structures of hypothetical trihelix DBDs of the wild-type (WT) and a phosphomimetic mutant (T133D) of GT-1. First, we demonstrated that the isolated DBD of GT-1 alone has the ability to bind to DNA, and that the T133D mutation of the isolated DBD can enhance the DNA-binding affinity. The structures of these DBDs turned out to be almost identical. The structural topology resembles that of Myb DBDs, but all alpha-helices are longer in GT-1. Our NMR titration experiments suggested that these longer alpha-helices yield an enlarged DNA-binding surface. The phosphorylation site is located at the N-terminus of the third alpha-helix. We built a structural model of the T133D DBD: BoxII complex with the program HADDOCK. The model resembles the structure of the TRF1 DBD: telomeric DNA complex. Interestingly, the model implies that the phosphorylated side chain may directly interact with the bases of DNA. On the basis of our findings, we propose a mechanism by which the DNA-binding activity toward BoxII of the phosphorylated GT-1 could be enhanced.
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