Plant Transcription Factor Database
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A homeobox (HB) encodes a protein domain, the homeodomain (HD), which is a conserved 60-amino acid motif present in transcription factors found in all the eukaryotic organisms. This 60-amino acid sequence folds into a characteristic three-helix structure that is able to interact specifically with DNA. Most HDs are able to bind DNA as monomers with high affinity, through interactions made by helix III (the so-called recognition helix) and a disordered N-terminal arm located beyond helix I. The high degree of conservation of this type of domain among diverse proteins from different kingdoms indicates that this structure is crucial to maintain the HD functionality and that the role played by this domain is vital.
Ariel FD, Manavella PA, Dezar CA, Chan RL.
The true story of the HD-Zip family.
Trends Plant Sci, 2007. 12(9): p. 419-26.
The PHD finger, a Cys4-His-Cys3 zinc finger, is found in many regulatory proteins from plants or animals which are frequently associated with chromatin-mediated transcriptional regulation. We show here that the PHD finger activates transcription in yeast, plant and animal cells. In plant homeodomain transcription factors the PHD finger is combined with an upstream leucine zipper. Both domains together form a highly conserved 180 amino acid region called the ZIP/PHDf motif and transcriptional activity of the PHD finger is masked when embedded in this motif. Our results indicate that the ZIP/PHDf domain is a potential regulatory domain of PHDf-HD proteins.
Halbach T, Scheer N, Werr W.
Transcriptional activation by the PHD finger is inhibited through an adjacent leucine zipper that binds 14-3-3 proteins.
Nucleic Acids Res, 2000. 28(18): p. 3542-50.