| Type: | Domain | Name: | ZF-HD homeobox protein, Cys/His-rich dimerisation domain |
| Description: | The homeodomain (HD) is a 60-amino acid DNA-binding domain found in many transcription factors. HD-containing proteins are found indiverse 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 orexclusively in floral tissue, indicating a likely regulatory role during floral development []. The ZF-HD class of homeodomain proteins may also beinvolved in the photosynthesis-related mesophyll-specific gene expression of phosphoenolpyruvate carboxylase in C4 species [] and in pathogen signalingand plant defense mechanisms []. These proteins share three domains of high sequence similarity: the homeodomain (II) located at the carboxy-terminus, and two other segments (Iaand Ib) located in the amino-terminal part. These N-terminal domains contain five conserved cysteine residues and at least three conserved histidineresidues whose spacing ressembles zinc-binding domains involved in dimerization of transcription factors. Although the two domains contain atleast eight potential zinc-binding amino-acids, the unique spacing of the conserved cysteine and histidine residues within domain Ib suggests that bothdomains form one rather than two zinc finger structures. The two conserved motifs Ia and Ib constitute a dimerization domain which is sufficient for theformation of homo- and heterodimers []. This entry represents the N-terminal Cysteine/Histidine-rich dimerization domain. The companion ZF-HD homeobox domain is described in . | Short Name: | ZF_HD_homeobox_Cys/His_dimer |
