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Figure 2.
Figure 2. Structure of Xenopus SANT. (A) A dimer of SANT domain
formed in the crystallographic asymmetric unit. The dimer
interface is formed between the N-terminal Pro-rich
loop--hydrophobic interactions involving proline residues (P743,
P746, P748, and P749) and helix  A
(Tyr775 and Tyr781) - and the helix D
(two salt bridges between invariant Arg803 of one protomer and
invariant Asp804 of another protomer). The Stokes radius of the
domain was consistent with a solution dimer: the 21-kDa protein
eluted from S75 gel filtration column with apparent molecular
weight of 41 kDa. The total area of dimer interface of 707
Å^2 is within the limits, though at the lower end, of the
32 homodimers examined.[9] (B) A 90° rotated view from panel
A. A Mg^2+ ion, required for crystallization, is bound at the
loop region between helices E
and F.
Three main chain carbonyl oxygen atoms of Ala852, Val855, and
Lys858 and two water molecules (w) coordinate the metal atom.
(C) GRASP surface charge distribution is displayed with blue for
positive, red for negative, and white for neutral. Filled circle
indicates the opening of the concave L-surface. (D) Three views
of the monomer structure of Xenopus SANT domain.
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