InterPro: IPR003656 Zinc finger, BED-type predicted

Zinc finger (Znf) domains are relatively small protein motifs which contain multiple finger-like protrusions that make tandem contacts with their target molecule. Some of these domains bind zinc, but many do not; instead binding other metals such as iron, or no metal at all. For example, some family members form salt bridges to stabilise the finger-like folds. They were first identified as a DNA-binding motif in transcription factor TFIIIA from Xenopus laevis (African clawed frog), however they are now recognised to bind DNA, RNA, protein and/or lipid substrates [1, 2, 3, 4, 5]. Their binding properties depend on the amino acid sequence of the finger domains and of the linker between fingers, as well as on the higher-order structures and the number of fingers. Znf domains are often found in clusters, where fingers can have different binding specificities. There are many superfamilies of Znf motifs, varying in both sequence and structure. They display considerable versatility in binding modes, even between members of the same class (e.g. some bind DNA, others protein), suggesting that Znf motifs are stable scaffolds that have evolved specialised functions. For example, Znf-containing proteins function in gene transcription, translation, mRNA trafficking, cytoskeleton organisation, epithelial development, cell adhesion, protein folding, chromatin remodelling and zinc sensing, to name but a few [6]. Zinc-binding motifs are stable structures, and they rarely undergo conformational changes upon binding their target.

This entry represents predicted BED-type zinc finger domains. The BED finger which was named after the Drosophila proteins BEAF and DREF, is found in one or more copies in cellular regulatory factors and transposases from plants, animals and fungi. The BED finger is an about 50 to 60 amino acid residues domain that contains a characteristic motif with two highly conserved aromatic positions, as well as a shared pattern of cysteines and histidines that is predicted to form a zinc finger. As diverse BED fingers are able to bind DNA, it has been suggested that DNA-binding is the general function of this domain [7]. Some proteins known to contain a BED domain include animal, plant and fungi AC1 and Hobo-like transposases; Caenorhabditis elegans Dpy-20 protein, a predicted cuticular gene transcriptional regulator; Drosophila BEAF (boundary element-associated factor), thought to be involved in chromatin insulation; Drosophila DREF, a transcriptional regulator for S-phase genes; and tobacco 3AF1 and tomato E4/E8-BP1, light- and ethylene-regulated DNA binding proteins that contain two BED fingers.

More information about these proteins can be found at Protein of the Month: Zinc Fingers [8].