Volume 11, Issue 11, Pages 1393-1402 (November 2003) The Zinc Finger-Associated Domain of the Drosophila Transcription Factor Grauzone Is a Novel Zinc-Coordinating Protein-Protein Interaction Module  Ralf Jauch, Gleb P Bourenkov, Ho-Ryun Chung, Henning Urlaub, Ulrich Reidt, Herbert Jäckle, Markus C Wahl  Structure  Volume 11, Issue 11, Pages 1393-1402 (November 2003) DOI: 10.1016/j.str.2003.09.015

Figure 1 ZAD as a Zinc-Coordinating Fold (A) Alignment of the Grauzone ZAD with its closest paralog, CG15073, in the Drosophila melanogaster genome and with a putative Anopheles gambiae homolog (ZAD only fragment, see Experimental Procedures). Asterisks mark 100% conservation in all three ZADs; red characters, invariant cysteine pairs; yellow boxes, conserved hydrophobic or aromatic amino acid residues. (B) Portion of ZADGrau remaining soluble after incubation at the indicated temperatures in the absence (−EDTA) and in the presence of 5 mM EDTA (+EDTA). Reduction of the soluble fraction is clearly visible when ZADGrau is heated above 50°C in presence of the chelator. (C) X-ray emission spectrum of a native ZADGrau crystal irradiated with X-radiation of λ = 1.0 Å. I, ZnKα line; II, ZnKβ line; III, Compton scattering; IV, elastic scattering. (D) Electron density maps around the zinc center in ZADGrau. Cyan, experimental MAD electron density map (1 σ); magenta, anomalous difference Fourier map (10 σ), generated with the anomalous differences at the peak wavelength and the phases obtained after solvent flattening. The zinc-coordinating cysteine residues are labeled and shown in ball-and-stick. If not mentioned otherwise, all structural figures were prepared with Bobscript (http://www.strubi.ox.ac.uk/bobscript/) and rendered with Raster3D (Merritt and Bacon, 1997). Structure 2003 11, 1393-1402DOI: (10.1016/j.str.2003.09.015)

Figure 2 ZAD Structure and Topology (A and B) Two orthogonal stereo ribbon plots of the ZADGrau structure. α helices, red; β strands, blue; loops, gold. In the side view of (A), the structure resembles the letter “b.” N- and C termini, secondary structure elements, and residues of the zinc center are labeled. The Zn2+ ion (green) and its coordinating cysteine side chains are shown in ball-and-stick. Structure 2003 11, 1393-1402DOI: (10.1016/j.str.2003.09.015)

Figure 3 Structural Comparison Ribbon (A) and electrostatic surface representation (B) of ZADGrau (left panels) and the C-terminal TCZF from chicken GATA-1 (right panels). Color coding for the ribbon plot is as in Figure 2. In the surface plot, red indicates negative potential, blue positive potential. The orientation is the same as in Figure 2B. This and all other surface images were prepared with SwissPDBViewer (Guex and Peitsch, 1997). Structure 2003 11, 1393-1402DOI: (10.1016/j.str.2003.09.015)

Figure 4 The ZADGrau Dimer (A) Stereo ribbon plot of a ZADGrau dimer as seen in the crystal. The two subunits (Mol I and Mol II) are colored red and blue; the two zinc centers are depicted in ball-and-stick. N- and C termini are labeled. The orientation of the rear subunit is the same as in Figure 2A. (B) Stereo representation of residue interactions in the dimer interface, 90° from the view in (A). The two ZADGrau subunits are colored as in (A) but are rendered semitransparent to clearly reveal the interacting residues in ball-and-stick. All residues and the molecular termini are labeled. (C) Mapping of the contact residues within the dimer (green) onto the surface of a ZADGrau monomer (gray). The orientation of the molecule is the same as that of the red subunit in (A). (D) Mapping in orange of conserved residues on the surface of ZADGrau in two diametric views. The left orientation is the same as in (C), indicating that the largest conserved surface patch and the dimer interface largely coincide. Structure 2003 11, 1393-1402DOI: (10.1016/j.str.2003.09.015)

Figure 5 Detection of ZADGrau Dimers in Solution (A) Results from chemical crosslinking with glutaraldehyde displayed on a denaturing polyacrylamide gel. Crosslinking took place for the times indicated above the lanes. SNAP-25 served as a negative control, GST as a positive control. Molecular weight markers are given on the left (kDa). (B) Results from a gel filtration chromatography run combined with multiangle-laser-light scattering analysis of the emerging peak. Emergence of protein from the column was detected by absorbance at 280 nm (black trace, left y axis), readout from the light scattering of the single, symmetrical peak is depicted as a gray line (right y axis). Structure 2003 11, 1393-1402DOI: (10.1016/j.str.2003.09.015)