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Solution Structure of a Zap1 Zinc Responsive Domain Provides Insights into Metalloregulatory Transcriptional Repression in S. cerevisiae
Author(s) -
Laity John H,
Wang Zhonghua,
Feng Linda S,
Matskevich Viktor A,
Venkataraman Krishna
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a994-c
Subject(s) - zinc , zinc finger , transcription factor , psychological repression , biology , biophysics , chemistry , crystallography , biochemistry , gene , gene expression , organic chemistry
The Zap1 transcription factor regulates zinc homeostasis genes in S. cerevisiae . The solution structure of two interacting C 2 H 2 zinc fingers (zf1‐2 CA3 ) derived from a zinc‐responsive domain of Zap1 (zf1‐2) is Inulin extracted from the chicory root contains linear fructans with degree of polymerisation (DP) between 3 and 65. Oligofructose is a partial hydrolysate (DP 2–8). Oligofruc‐tose and HP‐inulin (DP10‐65) are combined into Synergy1. Synergy1 suppresses carcinogenesis significantly more (Verghese in the press) reported. Under zinc‐limiting conditions, finger 2 (zf2) has been shown to act as a constitutive transcriptional activator. Moreover, repression of zf2 function in zinc‐replete cells required zinc coordination to both zf1‐2 metal sites, suggesting zf1‐zf2 cooperativity underlies Zap1 metalloregulation. A structural basis for this cooperativity is identified. Favorable inter‐helical contacts in zf1‐2 CA3 extend the individual finger hydrophobic cores through the zf1‐zf2 interface. Trp residues in each finger also provide non‐helical inter‐finger contacts. NMR and CD studies further reveal that zf1 independently forms a ββα structure, in contrast to zf2, which does not fold without zf1‐zf2 interactions. Cooperative effects on zf1 and zf2 Zn(II) affinities are also observed from calorimetric studies. We propose a mechanism for Zap1 transcriptional repression in which zf1‐zf2 interactions stabilize the ββα folded zf2 activation domain in the presence of cellular Zn(II) excess. In contrast to earlier reports of << 1 labile zinc ion per E. coli cell, the zf1‐2 zinc affinities determined calorimetrically are consistent with Zn(II) levels >> 1 labile zinc ion per eukaryotic cell.