1zw8 | pdb_00001zw8
Solution structure of a ZAP1 zinc-responsive domain provides insights into metalloregulatory transcriptional repression in Saccharomyces cerevisiae
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Overview
The Zap1 transcription factor controls expression of genes that regulate, zinc homeostasis in Saccharomyces cerevisiae. The solution structure of, two zinc fingers (zf1-2(CA3)) derived from a zinc-responsive domain of, Zap1 (zf1-2) has been determined. Under zinc-limiting conditions, zinc, finger 2 (zf2) from this domain has been shown to be a constitutive, transcriptional activator. Moreover, repression of zf2 function in, zinc-replete cells required zinc coordination to both canonical finger 1, (zf1) and zf2 metal sites, suggesting zf1-zf2 cooperativity underlies Zap1, metalloregulation. A structural basis for this cooperativity is identified, here. Favorable inter-helical contacts in zf1-2(CA3) extend the individual, finger hydrophobic cores through the zf1-zf2 interface. Tryptophan, residues at position 5 in each finger provide numerous non-helical, inter-finger contacts reminiscent of those observed in GLI1 zinc fingers 1, and 2. The molecular mechanism for zf1-dependent repression of zf2, transcriptional activation is explored further using NMR and CD titration, studies. While zf1 independently forms a betabetaalpha solution structure, the majority of zf2 ensemble solution states do not adopt the canonical, betabetaalpha zinc finger fold without zf1-zf2 interactions. Cooperative, effects on Zn(II) affinities stemming from these finger-finger, interactions are observed also in calorimetric studies, in which the, 160(+/-20)nM (zf1) and 250(+/-40)nM (zf2) K(d) values for each individual, finger increased substantially in the context of the zf1-2 protein, (apparent K(dzf1-2WT)=4.6(+/-1.2)nM). On the basis of the above, observations, we propose a mechanism for Zap1 transcriptional regulation, in which zf1-zf2 interactions stabilize the betabetaalpha folded, "repressed state" of the zf2 activation domain in the presence of cellular, Zn(II) excess. Moreover, in contrast to earlier reports of <<1 labile zinc, ion/Escherichia coli cell, the zf1-zf2 zinc affinities determined, calorimetrically are consistent with Zn(II) levels >>1 labile zinc, ion/eukaryotic cell.
About this Structure
1ZW8 is a Single protein structure of sequence from Saccharomyces cerevisiae with ZN as ligand. Full crystallographic information is available from OCA.
Reference
Solution structure of a Zap1 zinc-responsive domain provides insights into metalloregulatory transcriptional repression in Saccharomyces cerevisiae., Wang Z, Feng LS, Matskevich V, Venkataraman K, Parasuram P, Laity JH, J Mol Biol. 2006 Apr 7;357(4):1167-83. Epub 2006 Jan 24. PMID:16483601
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