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PDBsum entry 1wko
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Signaling protein
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PDB id
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1wko
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References listed in PDB file
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Key reference
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Title
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A divergent external loop confers antagonistic activity on floral regulators ft and tfl1.
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Authors
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J.H.Ahn,
D.Miller,
V.J.Winter,
M.J.Banfield,
J.H.Lee,
S.Y.Yoo,
S.R.Henz,
R.L.Brady,
D.Weigel.
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Ref.
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Embo J, 2006,
25,
605-614.
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PubMed id
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Abstract
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The Arabidopsis genes FT and TERMINAL FLOWER1 (TFL1) encode related proteins
with similarity to human Raf kinase inhibitor protein. FT, and likely also TFL1,
is recruited to the promoters of floral genes through interaction with FD, a
bZIP transcription factor. FT, however, induces flowering, while TFL1 represses
flowering. Residues responsible for the opposite activities of FT and TFL1 were
mapped by examining plants that overexpress chimeric proteins. A region
important in vivo localizes to a 14-amino-acid segment that evolves very rapidly
in TFL1 orthologs, but is almost invariant in FT orthologs. Crystal structures
show that this segment forms an external loop of variable conformation. The only
residue unambiguously distinguishing the FT and TFL1 loops makes a hydrogen bond
with a residue near the entrance of a potential ligand-binding pocket in TFL1,
but not in FT. This pocket is contacted by a C-terminal peptide, which also
contributes to the opposite FT and TFL1 activities. In combination, these
results identify a molecular surface likely to be recognized by FT- and/or
TFL1-specific interactors.
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