Protein zinc finger variants

Fig. 2. Examples of the structures of protein domains and repeats. The images were generated using Molscript (Kraulis, 1991). (A) Immunoglobulin domain (PDB identifier ltlk) (Holden et al1992), (B) A zinc finger domain with coordinated zinc ion (PDB identifienlzaa) (Pavletich and Pabo, 1991). (C) A /3-propeller domain composed of seven WD40 repeats (PDB identifier lgp2) (Wall et al., 1995), (D) An elongated domain of variant leucine-rich repeats (PDB identifienllrv) (Peters et al., 1996).

The EXAFS studies of zinc finger proteins, TFIIIA (33) and the glucocorticoid receptor (34), show clearly that there is not a unique environment for zinc in these systems (Fig. 4). Zinc bound to two histidine and two cysteine residues or four cysteinyl residues suggests that variants within the subset Zn(histidine)4-x(cysteine)j (x = 0-4) should be considered. Also, the possibility implied by the GAL4 results, that the zinc sites may have some substitutional lability, raises further questions as to the role of zinc in the transcription of the genetic information stored in DNA. 

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