InterPro domain: IPR006456

The homeodomain (HD) is a 60-amino acid DNA-binding domain found in manytranscription 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 playplant specific roles. ZF-HD proteins are expressed predominantly orexclusively in floral tissue, indicating a likely regulatory role duringfloral development [ 1 ]. The ZF-HD class of homeodomain proteins may also beinvolved in the photosynthesis-related mesophyll-specific gene expression ofphosphoenolpyruvate carboxylase in C4 species [ 2 ] and in pathogen signalingand plant defense mechanisms [ 3 ].

These proteins share three domains of high sequence similarity: thehomeodomain (II) located at the carboxy-terminus, and two other segments (Iaand Ib) located in the amino-terminal part. These N-terminal domains containfive conserved cysteine residues and at least three conserved histidineresidues whose spacing ressembles zinc-binding domains involved indimerization of transcription factors. Although the two domains contain atleast eight potential zinc-binding amino-acids, the unique spacing of theconserved cysteine and histidine residues within domain Ib suggests that bothdomains form one rather than two zinc finger structures. The two conservedmotifs Ia and Ib constitute a dimerization domain which is sufficient for theformation of homo- and heterodimers [ 4 ].

This entry represents the N-terminal Cysteine/Histidine-rich dimerization domain. The companion ZF-HD homeobox domain is described in IPR006455 .

1. The Arabidopsis zinc finger-homeodomain genes encode proteins with unique biochemical properties that are coordinately expressed during floral development. Plant Physiol. 140, 1095-108
2. Characterization of a novel class of plant homeodomain proteins that bind to the C4 phosphoenolpyruvate carboxylase gene of Flaveria trinervia. Plant Mol. Biol. 45, 201-14
3. Pathogen-induced binding of the soybean zinc finger homeodomain proteins GmZF-HD1 and GmZF-HD2 to two repeats of ATTA homeodomain binding site in the calmodulin isoform 4 (GmCaM4) promoter. Nucleic Acids Res. 35, 3612-23