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Figure 3.
Figure 3. Structure of RFCS Hexamers(A) Comparison of a
hypothetical hexameric ring of RFCS (center) with the electron
microscopic image (left). The 6-fold symmetry ring model was
built from a semicircular trimer of RFCS in the crystal (right)
and is drawn in top (upper) and side views (lower). One subunit
in each hexamer is encircled. The EM 3D reconstructed images
were obtained by essentially the same procedure as in our
previous study (Mayanagi et al., 2001; K. Mayanagi and T.
Miyata, personal communication). The scale bar indicated for the
EM images is 50 Å.(B) Interaction scheme between subunits
within the semicircular trimers, represented by an open-book
view. Subunits with interfaces near the convex side of the
crescent-shaped molecules are designated as “front,” while
those with interfaces at the inner concave region of the
crescents are designated as “back.” Only MolA and MolB are
drawn as representative subunits. Segments contributing to the
interfaces are colored blue for the front subunit and magenta
for the back. In the front subunit, four segments, residues
4–14, 206–210, 229–231, and 262–271, contribute to
Interface I (upper half), while two segments, residues 249–255
and 300–323, form Interface II (lower half). In the back
subunit, residues 36–47 and 149–168 are involved in
Interface I and residues 277–309 in Interface II. Intersubunit
hydrogen bonding and hydrophobic interactions, which are
observed in more than two interfaces of the total four, are
indicated by red and green lines, respectively
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