| Description: |
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 [, , , , ]. 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 []. Zinc-binding motifs are stable structures, and they rarely undergo conformational changes upon binding their target. These sequences contain a putative zinc finger domain found predominantly in plants. Arabidopsis thaliana (Mouse-ear cress) has at least 10 distinct members. Proteins containing this domain, including LRP1 (lateral root primordium 1)[], generally share the same size, about 300 amino acids, and architecture. This 43-residue domain, and a more C-terminal companion domain of similar size, appear as tightly conserved islands of sequence similarity. The remainder consists largely of low-complexity sequence. Several animal proteins have regions with matching patterns of Cys, Gly, and His residues. But are excluded from this family because of their low similarity. |
