Eukaryotes zinc finger proteins

Zinc-fingers are common in DNA-binding proteins of eukaryotes but are not found in prokaryotes. Examples of zinc-finger proteins include the RNA polymerase III transcription factor TFIIIA, steroid receptors, and some gene products that control development. The zinc-finger consists of pairs of cysteine and/or histidine residues within an a-helix. These residues bind tightly to a Zn2+ ion, which allows the a-helical amino acids to interact with specific sequences. See Figure 12-18. 

Zinc-Finger Proteins A number of different eukaryotic proteins have regions that fold around a central Zn ion, producing a compact domain from a relatively short length of the polypeptide chain. Termed a zinc finger, this structural motif was first recognized in DNA-binding domains but now... 

Zinc, in addition to its use as a Lewis acid in enzyme catalysis, plays a structural role in stabilizing protein molecules. It is also involved in a characteristic motif, termed zinc finger, in a number of eukaryotic DNA-binding proteins (that regulate the transcription of DNA into RNA), first described by Aaron Klug. 

Several DNA-binding motifs have been described, but here we focus on two that play prominent roles in the binding of DNA by regulatory proteins the helix-tum-helix and the zinc finger. We also consider a type of DNA-binding domain—the homeodomain—found in some eukaryotic proteins. 

The precise manner in which proteins with zinc fingers bind to DNA differs from one protein to the next. Some zinc fingers contain the amino acid residues that are important in sequence discrimination, whereas others appear to bind DNA nonspecifically (the amino acids required for specificity are located elsewhere in the protein). Zinc fingers can also function as RNA-binding motifs—for example, in certain proteins that bind eukaryotic mRNAs and act as translational repressors. We discuss this role later (Section 28.3). 

DNA-Binding Proteins that Regulate Transcription in Eukaryotes Are Often Asymmetrical The Homeodomain Zinc Finger Leucine Zipper Helix-Loop-Helix... 

Another DNA-binding motif very common in eukaryotic regulatory proteins is the zinc finger. This motif was first identified as the DNA-binding structure in the RNA poly-... 

The most striking difference between DNA-binding proteins in prokaryotes and eukaryotes has to do with the symmetry of the interaction. In prokaryotes the binding proteins almost always interact in a symmetrical fashion with the DNA. In eukaryotes most of the cases that have been examined so far involve proteins that interact in an asymmetrical fashion with the DNA. In many cases the regulatory proteins interact in multisubunit complexes that contain nonidentical subunits. Four different types of structural motifs are discussed The homeodomain, the zinc finger, the leucine zipper, and the helix-loop-helix. 

Struhl, K., Helix-tum-helix, zinc-finger and leucine-zipper motifs for eukaryotic transcriptional regulatory proteins. 

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