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Figure 5.
FIG. 5. Structural models of the dynein stalk. A, models of
a section of the dynein stalk in configurations expected to
correspond to those occurring in SRS-22:19 or SRS19:19. CC2 is
shown in surface representation with hydrophobic residues (Val,
Ile, Leu, Ala, Met, Tyr) in the coiled-coil core ("a" and "d"
positions) colored green. CC1 is shown in backbone
representation (gray) with side chains included for Ser-3224
(yellow), Leu-3227 (cyan; with asterisk) and Lys-3230 (magenta).
In passing from the configuration of SRS-22:19 to that of
SRS-19:19, the side chain of Leu-3227 shifts from packing
against one side of CC2 (left) to packing against the other side
(right), potentially by following the hydrophobic-lined groove
formed by Ile-3459, Leu-3463, Val-3466 and Val-3470 in the
surface of CC2 (dashed line). Similar hydrophobic grooves in the
core interface of CC2 occur in most other heptads along the
length of the stalk coiled coil (supplemental material). B,
schematics depicting transverse sections through the coiled-coil
stalk in the region shown in A. Residues in CC1 are colored as
in A to illustrate that Leu-3227 (cyan) shifts from a "d" heptad
position to an "a" position in going between the 22:19 and 19:19
configurations (see also Fig. 2A). Panel A of this figure was
prepared with the program MOLMOL (22). Coordinates of these
models have been deposited in the theoretical models section of
the Protein Data Bank under the identifiers 2BOT (SRS-22:19) and
2BOR (SRS-19:19).
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