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Figure 5.
Structure of Asn-hydroxylated N1 ARD.A, stereoview ribbon
representation from the 2.35 Å resolution crystal
structure of N1 ARD (OH); six ARs (numbered 2–7) are observed
in the N1 ARD (OH) structure. The hydroxylated Asn-1945 (AR 2)
and unhydroxylated Asn-2012 (AR 4) are yellow ball-and-stick
representations. B, stereoview of electron density around
Asn-1945 showing the pro-S configuration of the hydroxylated
Asn-1945 β-carbon. 2F[o] - F[c] map (cyan mesh) contoured to
1σ and an F[o] - F[c] OMIT map (dark blue mesh) contoured to
5σ (produced by omitting the hydroxyl group from the
calculation). This region of the β-hairpin loop has a type I
β-turn (Asp-1943, Ala-1944, Asn-1945, and Ile-1946 at the i, i
+ 1, i + 2, and i + 3 positions, respectively). Asn-1945 makes
three hydrogen bonds (dashed black lines); the nitrogen and
oxygen of the side chain amide form hydrogen bonds to the
backbone carbonyl oxygen of Ala-1975 and NH of Asp-1977, and the
β-hydroxy group hydrogen bonds with an Asp-1943 carboxylate
oxygen. C, ribbon representation of the Asn-1945 hydroxylated
mN1-(1898–2105) (blue) and the MAML-1 (green)·human
N1-(1873–2127) (purple)·CSL
(yellow/beige/orange)·DNA (blue) complex (Protein Data
Bank code 2F8X) structures (24) superimposed.
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