Figure 4.
Figure 4. Various crystalline oligomers of Pae and Mth
SmAP1. A unit cell of the Pae SmAP1 C222[1] crystal form is
shown in (A), along with examples of crystallographic twofold
and 2[1] screw axes. The asymmetric unit is a heptamer (shown as
C traces in red
or blue), and a Pae SmAP1 14-mer with 72-point group symmetry is
formed from adjacent asymmetric units (7550 Å2 of surface area
is buried at the heptamer-heptamer interface). Orthogonal views
of the quasihexagonal packing of Mth SmAP1 heptamers in the
P2[1]2[1]2[1] crystal form are shown in (B). Heptamers stack
upon one another to form cylindrical tubes, thus providing a
model for the structure of the EM fibrils (see text for
explanation). The head-to-tail association of heptamers gives
the tubes a defined polarity (colored arrows). Molecular
surfaces show that the lateral packing of tubes in the crystal
may generate the striated bundles seen by EM.
The above figure is reprinted
by permission from the Protein Society:
Protein Sci
(2003,
12,
832-847)
copyright 2003.
traces in red
or blue), and a Pae SmAP1 14-mer with 72-point group symmetry is
formed from adjacent asymmetric units (7550 Å2 of surface area
is buried at the heptamer-heptamer interface). Orthogonal views
of the quasihexagonal packing of Mth SmAP1 heptamers in the
P2[1]2[1]2[1] crystal form are shown in (B). Heptamers stack
upon one another to form cylindrical tubes, thus providing a
model for the structure of the EM fibrils (see text for
explanation). The head-to-tail association of heptamers gives
the tubes a defined polarity (colored arrows). Molecular
surfaces show that the lateral packing of tubes in the crystal
may generate the striated bundles seen by EM.