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Figure 4.
Figure 4. Stereoscopic view of the intercalation sites. The
local structures of the two Sso−DNA complexes are
superimposed. The DNA octamer is kinked 61° at the C2pG3
step in the Sso7d−GCGT(^ iU)CGC + GCGAACGC complex and 62°
at the A3−A4 step in the Sso7d−GTAATTAC complex. The sharp
kink is due to the intercalation of Val 26 and Met 29 amino acid
side chains into DNA base pairs from the minor groove direction,
widening the minor groove at this step. The insertions of  4-Met
29 and 3-Val
26 amino acid side chains are ~1.5 Å deep. The side chain
of Met 29 lies close to the base pair with the S-CH[ 3] moiety
wedged between the C14 and G15 bases. Similarly the side chain
of Val 26 is wedged between the C2 and G3 bases, with each of
the  CH[
3] groups pointing toward a base.
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