Zinc, cobalt and cadmium thiolate complexes: Models for the Zn(S-cys)3(his) center in the gene 32 protein

Corwin, Douglas T.; Gruff, Eric S.; Koch, Stephen A.

doi:10.1016/s0020-1693(00)83473-8

Cited by 28 publications

(21 citation statements)

References 10 publications

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“…coefficients for these bands of -500 M-1cm-1 are most consistent with a tetrahedral site (62). This conclusion is supported by recent studies of four-and five-coordinate complexes of Co2+ with nitrogen and sulfur ligands (63,64). The spectrum also includes charge transfer bands indicative of metal-cysteinate coordination.…”

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confidence: 76%

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A retroviral Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys peptide binds metal ions: spectroscopic studies and a proposed three-dimensional structure.

Green

Berg

1989

Proc. Natl. Acad. Sci. U.S.A.

159

120

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Retroviral gag gene-encoded core nucleic acid binding proteins contain either one or two sequences of the form Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys. Previously, one of us has proposed that these sequences form metal-binding domains in analogy with the "zinc ringer" domains first observed in transcription factor MA. We report that an 18-amino acid peptide derived from the core nucleic acid binding protein from Rauscher murine leukemia virus binds metal ions such as Co2' and Zn2+. The absorption spectrum of the peptide-Co2 complex is highly suggestive of tetrahedral coordination involving three cysteinates and one histidine. Titration experiments indicate that the dissociation constant for the peptideCo2+ complex is 1.0 ,uM and that Zn2+ binds more tightly than Co2+. A detailed three-dimensional structure for this domain based on conserved substructures in other crystallographically characterized metalloproteins and on a detailed analysis of the Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys sequences from retroviruses and other related sources is proposed.In 1985, two groups observed the occurrence of nine tandem sequences of the form Cys-Xaa4-Cys-Xaa12-His-Xaa3-His in the deduced amino acid sequence of Xenopus transcription factor IIIA (TFIIIA) (1,2). Based on the presence of zinc in a purified TFIIIA-5S RNA complex (1, 3), it was proposed that each of these sequences forms a metal-binding domainthat is, a relatively discrete structural unit stabilized by the tetrahedral coordination of a zinc ion to the invariant cysteine and histidine residues. These domains were termed "zinc fingers" (1). Subsequently, numerous other deduced protein sequences have been found that contain quite similar sequences that match the template described above (4-6).Where it is known, the function of these proteins is to act as specific nucleic acid binding proteins. Studies with several proteins have revealed that zinc is required for this activity (3,(7)(8)(9). The hypothesis that these sequences do indeed form metal-binding domains has been amply supported by a wide variety ofmethods including limited proteolysis studies ofthe TFIIIA-SS RNA complex (1), extended x-ray absorption fine structure spectroscopic studies of the zinc sites in the TF-IIIA-5S RNA complex (10), studies of the structure of the TFIIIA gene (11), hydroxyl radical footprinting studies of a series of shortened versions of TFIIIA on a 5S RNA gene (12), and studies of single domain peptides (13,14 (20) that appear to share the property that they undergo a reverse transcription step at some point in their life cycles (21). The importance ofthe conserved cysteine and histidine residues for viral replication has been directly demonstrated by site-directed mutagenesis in two systems (22,23). Results obtained by using a radioactive zinc blotting technique indicated that these proteins have an affinity for zinc under certain conditions (24). We report herein that an 18-amino acid sequence Asp-Gln-Cys-Ala-Tyr-Cys-Lys-Glu-LysGly-His-Trp-Ala-Lys-Asp-Cys-Pro-Lys derived from the sequence o...

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confidence: 76%

“…In addition, the charge transfer bands appear at somewhat lower energies. Importantly, these differences are similar to the differences between the spectra of Co(SR)3(NMeIm)-and Co(SR)2(N-MeIm)2 where SR represents a substituted benzenethiolate and N-MeIm is 1-methylimidazole (64).…”

supporting

confidence: 64%

A retroviral Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys peptide binds metal ions: spectroscopic studies and a proposed three-dimensional structure.

Green

Berg

1989

Proc. Natl. Acad. Sci. U.S.A.

159

120

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“…Furthermore, the increased intensity of the ligand field absorption bands at higher wavelengths in the E⅐I a ⅐TKCVIM complex compared with those in the E⅐I a binary complex is also consistent with additional coordinating thiolates (15,(27)(28)(29). Finally, the increased extinction coefficient of the d-d transition maximum at 635 nm (⑀ 635 ϭ 310 M Ϫ1 cm Ϫ1 ) is typical of a cobalt binding site with tetrahedral geometry (30).…”

Section: Absorption Spectra Of Ternary Complexes Of Co 2ϩmentioning

confidence: 55%

Evidence for a Catalytic Role of Zinc in Protein Farnesyltransferase

Huang

Casey

Fierke

1997

Journal of Biological Chemistry

155

124

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. These data provide evidence that the zinc ion plays an important catalytic role in FTase, most likely by activation of the cysteine thiol of the protein substrate for nucleophilic attack on the isoprenoid.Protein farnesyltransferase (FTase) 1 catalyzes the transfer of the farnesyl group of farnesyl pyrophosphate (FPP) to a conserved cysteine residue of a protein substrate, including Ras proteins, nuclear lamins, and several proteins involved in cell signaling (1-4). Protein farnesylation mediates membrane association and, possibly, interactions with other proteins essential for the localization and function of these proteins (3, 4). One example in this regard is the requirement of farnesylation for the cell transforming ability of oncogenic Ras proteins (5); this result has stimulated an intense search for FTase inhibitors as potential anticancer drugs (6, 7). An increased understanding of the molecular mechanism of FTase should enhance the rational design of such FTase inhibitors.FTase is a metalloenzyme that contains one zinc ion per ␣/␤ heterodimer that is essential for optimal activity (8, 9). Crosslinking and direct binding studies indicate that the zinc ion is required for the binding of protein but not isoprenoid substrates (8). Additionally, FTase containing Cd 2ϩ substituted for Zn 2ϩ has essentially normal catalytic activity, demonstrating that other metal ions can functionally substitute for the zinc (10). Chemical modification and site-directed mutagenesis studies have identified a conserved cysteine residue of FTase, Cys 299 , in the ␤ subunit, as important for catalytic activity and zinc binding, suggesting that the thiolate of this residue may directly coordinate the zinc ion (11).Although it is clear that the zinc ion in FTase is critical for activity, the precise function of the metal, particularly the question of whether the primary role of the zinc ion is structural or catalytic, is not yet known. Proposed catalytic functions for the zinc ion in FTase include increasing the nucleophilicity of the cysteine residue of the protein substrate (3,8,11,12) and/or activating the diphosphate leaving group (11,13,14). Here we investigate the metal coordination polyhedron in FTase by substituting Co 2ϩ for Zn 2ϩ , which does not change the catalytic activity of the enzyme. This substitution provides a useful spectroscopic probe of the composition and geometric arrangement of the ligands around the metal ion (15,16), and the spectral data obtained indicate that the metal ion coordinates the thiolate of the peptide substrate in the presence of bound FPP. EXPERIMENTAL PROCEDURESPreparation of Apo-FTase-Recombinant Rat FTase was produced and purified as described (9). Apo-FTase was prepared by dialyzing the holo-enzyme (Ͼ1 mg/ml) for 24 h against 50 mM Tris-Cl, pH 7.8, 1 mM tris(2-carboxyethyl)phosphine hydrochloride (TCEP) (Buffer 1) and 5 mM EDTA at 4°C followed by an additional 24 h dialysis against Buffer 1 containing 50 M EDTA. After dialysis, the apo-FTase was concentrated to ϳ100 M, flash-frozen, ...

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“…Finally, these single domain peptides have been quite useful for studies with spectro scopically active metal ions such as Co2+. The absorption spectra of Co 2 + -substituted single domain peptides (29,61) are entirely consistent with tetrahedral two cysteinate-two histidine coordination, especially when compared with appropriate model complexes (20,21). Perhaps the most direct evidence concerning the coordination environ ment around the zinc ions in TFIIIA comes from x-ray absorption studies of the TFIITA-5S RNA complex (23).…”

Section: In Tfiiiamentioning

confidence: 66%

Zinc Finger Domains: Hypotheses and Current Knowledge

Berg

1990

Annu. Rev. Biophys. Biophys. Chem.

306

132

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Many of the hypotheses are clearly correct that are based on the initial observation that TFIIIA has an approximately periodic structure with invariant pairs of cysteines and histidines apparently capable of coordinating metal ions. A startling number of other cDNA clones encode proteins that contain one or more sequences that match the zinc finger consensus, revealing that zinc finger proteins represent perhaps the largest class of DNA binding proteins in eukaryotes and that zinc finger protein-controlled gene expression may be a fundamental aspect of development as well as other processes. A great deal of progress has been made in elucidating the structure of single zinc finger domains. From knowledge of these structures, plausible and testable models can be developed for the complexes between zinc finger proteins and their DNA binding sites. Clearly, one of the most important challenges remaining in this area involves testing and extending these models. Structural data on such protein-nucleic acid complexes derived from NMR or crystallographic studies is tremendously valuable in this regard. Finally, an additional fundamental question is raised by the observation that this family and other important nucleic acid binding proteins contain zinc ions bound in small structural domains. Is zinc binding merely a useful structural strategy for generating domains involved in macromolecular interactions, or are zinc concentration fluctuations used in some manner to regulate gene expression? The biophysical data available to date certainly do not rule out this intriguing possibility.

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Zinc, cobalt and cadmium thiolate complexes: Models for the Zn(S-cys)3(his) center in the gene 32 protein

Cited by 28 publications

References 10 publications

A retroviral Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys peptide binds metal ions: spectroscopic studies and a proposed three-dimensional structure.

A retroviral Cys-Xaa2-Cys-Xaa4-His-Xaa4-Cys peptide binds metal ions: spectroscopic studies and a proposed three-dimensional structure.

Evidence for a Catalytic Role of Zinc in Protein Farnesyltransferase

Zinc Finger Domains: Hypotheses and Current Knowledge

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