Zinc fingers transcription factor IIIA

Fig. 9.1. Left panel A model zinc finger obtained using the second domain of the transcription factor IIIA. The zinc ion (gray sphere) is coordinated tetrahedrally by two histidine (H) and two cysteine (C) residues. Right panel Results showing the free energy change for displacing Zn2+ by other comparable ions Fe2+ and Co2+ from different binding motifs CCHH, CCHC, and CCCC, respectively...

Nolle, R. T, Conlin, R. M., Harrison, S. C. and Brown, R. S. (1998). Differing roles for zinc fingers in DNA recognition structure of a six-finger transcription factor IIIA complex. Proc. Nat. Acad. Set. USA 95,2938-2943. 

The principal impetus to the study of zinc thiolates has undoubtedly been the search for structural models for the metal coordination in zinc metalloproteins such as the Zn(S-Cys)2(His)2 center in the transcription factor IIIA and other zinc fingers that feature in protein-DNA interactions (93, 94). The 2 1 complexes [M(SR)2l (M = Zn, Cd SR = TIPT, TEMT) were used as the principle precursors for the synthesis of such models for the Zn(S-Cys)2(His)2. Thus complexes of the types [Cd(TIPT)2(l-CH3-imid)2], [Zn(TIPT)2(bipy)], and [Zn(TEMT)2(l-CH3-imid)2l (imid = imidazole, bipy = bipyridine) were ssmthesized by addition of a nitrogeneous base to the precursor in MeCN. All of them have been characterized by X-ray crystallography and were found to have distorted tetrahedral geometries. It was noticed that the cobalt analogue binds a solvent molecule MeCN to form five-coordinate [Co(TIPT)2(bipy)(CH3CN)], whereas [Zn(TIPT)2(bipy)] does not 96,97). 

Zinc Fingers The Role of Zinc(II) in Transcription Factor IIIA and Related Proteins... 

Zinc finger a DNA binding motif first recognized in Xenopus transcription factor IIIA (which binds to the internal control sequence of the 5S rRNA gene). This protein contains nine 30-residue sequences, all rather similar and arranged in tandem. Each contains two invariant Cys residues and two invariant His residues, as well as several conserved hydrophobic residues. Each of these structural domains folds about a single Zn ion, and X-ray analysis indicates that the zinc ion is tetrahedrally liganded by the invariant... 

FIGURE 2 Section of transcription factor iiia bound to DNA an exampie of zinc finger binding. 

The Xenopus 5S RNA gene-specific transcription factor IIIA (TFIIIA) was the first zinc finger protein characterized one decade ago (Klug and Rhodes 1987 Berg 1990 Rhodes and Klug 1993). This protein specifically binds to... 

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