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Figure 5.
Figure 5. The N-terminal domain rotates to accommodate
compression of the RecA filament. a, Two neighboring monomers in
the RecA filament are shown in yellow and cyan in an orientation
similar to that of the subunits on the front of the filaments
shown in Figure 2. This orientation is chosen to optimize the
visibility of the monomer-monomer interaction. Form 1 (PDB code
2REB)12 is shown in continuous lines and form 2 is shown in
broken lines. The form 1 and 2 structures are superimposed on
the basis of the C^a atoms of the core domains of the monomer on
the left. The difference in the helical transformation in forms
1 and 2 is evident from the poor overlap of the monomer on the
right. Residues 6 and 33 are labeled to indicate the boundaries
of the N-terminal domain. b, Close-up view of a in the region of
the monomer-monomer interface. Notice that the orientation of
the N-terminal domain of the left monomer is different in the
form 1 and form 2 structures, according to the position of the
neighboring subunit. The orientation of the N-terminal domain is
adjusted to accommodate changes in helical pitch, while
preserving atomic interactions at the monomer-monomer interface.
This is observed also in the form 3 and form 4 structures,
though shown here only for the form 1 and form 2 structures.
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