PROSITE documentation PDOC51523

Zinc-finger ZF-HD dimerization-type profile

The homeodomain (HD) is a 60-amino acid DNA-binding domain found in many transcription factors (see <PDOC00027>). HD-containing proteins are found in diverse organisms such as humans, Drosophila, nematode worms, and plants, where they play important roles in development. Zinc-finger-homeodomain (ZF-HD) subfamily proteins have only been identified in plants, and likely play plant specific roles. ZF-HD proteins are expressed predominantly or exclusively in floral tissue, indicating a likely regulatory role during floral development [1]. The ZF-HD class of homeodomain proteins may also be involved in the photosynthesis-related mesophyll-specific gene expression of phosphoenolpyruvate carboxylase in C4 species [2] and in pathogen signaling and plant defense mechanisms [3].

These proteins share three domains of high sequence similarity: the homeodomain (II) located at the carboxy-terminus, and two other segments (Ia and Ib) located in the amino-terminal part. These N-terminal domains contain five conserved cysteine residues and at least three conserved histidine residues whose spacing ressembles zinc-binding domains involved in dimerization of transcription factors. Although the two domains contain at least eight potential zinc-binding amino-acids, the unique spacing of the conserved cysteine and histidine residues within domain Ib suggests that both domains form one rather than two zinc finger structures. The two conserved motifs Ia and Ib constitute a dimerization domain which is sufficient for the formation of homo- and heterodimers [2].

The profile we developed covers the entire ZF-HD dimerization-type zinc finger.