Figure 2

Ribbon diagram of the STAT1 homodimer-DNA complex (PDB code:1bf5) and model of SUMO conjugated STAT1 dimer. (A) SUMO consensus element and amino acid (aa) sequence of SUMO-conjugation site in STAT1. The symbol ψ indicates large hydrophobic amino acid and x can be any amino acid. (B) Coiled-coil domain, DNA-binding domain and linker region of one monomer are colored green and the SH2 domain is colored in salmon red. SH2 domain of adjacent monomer is colored light yellow and other domains are blue. DNA strand is labelled and colored in red. Residues, pTyr701 (salmon red), Lys703 (red) and Glu705 (blue) are shown in a stick representation. All ribbon diagrams presented in Figure 2 are colored uniformly and produced using PyMOL (http://www.pymol.org). (C) The model of SUMO conjugated STAT1 was constructed by superimposing the X-ray structures of SUMO-1 from the complex of SUMO-1-TDG (PDB code:1wyw) and the structure of DNA bound STAT1 dimer (PDB code:1bf5). The molecular geometry of the loop 684–699 in the SH2 domain was calculated using the program Sybyl with Amber 7 FF99 force field parameters. Green and blue colours were used to distinguish monomers in a ribbon diagram of DNA bound STAT1 dimer. The loop and DNA are labeled and colored with red. The SUMO-1 was incorporated between the loop and DNA in conjugation distance on both sides of dimer. SUMO-1 is represented in ribbon and its molecular surface in yellow. Graphics were produced using PyMOL (http://www.pymol.org).