Figure 2.
Fig. 2. Structural basis for the splaying in the
C-terminal region of striated muscle Tm. (A) In the C-terminal
region of striated muscle -Tm, there
are three consecutive "core" residues (blue) that are generally
disfavored in two-stranded coiled coils: Gln-263 (d position),
Tyr-267 (a position), and Ile-270 (d position). The two
equivalent Ile side chains do not contact each other, and the
pairs of Gln and Tyr side chains do not display the usual
symmetric "knobs-into-holes" packing pattern. In each of these
two cases (B and C), only one of the two equivalent residues is
inserted into the hole on the opposite helix. Moreover, the
distance between the two helices increases to accommodate the
insertion of such long or bulky side chains.
-Tm, there
are three consecutive "core" residues (blue) that are generally
disfavored in two-stranded coiled coils: Gln-263 (d position),
Tyr-267 (a position), and Ile-270 (d position). The two
equivalent Ile side chains do not contact each other, and the
pairs of Gln and Tyr side chains do not display the usual
symmetric "knobs-into-holes" packing pattern. In each of these
two cases (B and C), only one of the two equivalent residues is
inserted into the hole on the opposite helix. Moreover, the
distance between the two helices increases to accommodate the
insertion of such long or bulky side chains.