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Figure 6.
FIGURE 6. Composite heparin binding site in the Slit-Robo
complex. Shown is a model of the human Slit2 D2-Robo1 IG1-2
complex, obtained by substituting Robo1 IG1 with crystal form 1
of Robo1 IG1-2 (14). A, surface representation: pale brown,
Robo1 IG1; pale green, Robo1 IG2; pale pink, Slit2 D2. B,
electrostatic surface representation of the same complex (red,
negative potential; blue, positive potential). The positions of
heparin binding residues in Slit D2 (21) and Robo IG1-2 (this
study) are labeled. Human Robo1 residues Lys-81, Arg-131,
Arg-136, and Lys-137 correspond, respectively, to Drosophila
Robo residues Lys-69, Arg-117, Lys-122, and Lys-123. The
location of the bound heparin oligosaccharide in the Robo IG1-2
structure is indicated by a semitransparent circle. A heparin
octasaccharide (dp8) and decasaccharide (dp10) are drawn to
scale and shown in ball-and-stick representation. HS/heparin is
suggested to bind to the extended basic surface across the
Slit-Robo interface (see text).
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