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Figure 1.
Fig. 1. The (PA[63])[7] prepore structure. (a) A single
monomer from the 3.6-Å (PA[63])[7] structure. Domains 1,
2, 3, and 4 are colored in pink, green, yellow and blue,
respectively. The previously unresolved 303-322 (red), 343-350
(blue) and 512-515 (blue) loops are visible whereas the 275-283
and 426-427 loops remain unstructured (black dotted lines). (b)
An aerial view (domain 1' is at the top, closest to the viewer)
of the PA[63] heptamer with one monomer colored as in a. Domain
2 lines the prepore lumen whereas domains 3 and 4 are located on
the outside of the heptamer ring. (c) Domains 2 (green) and 4
(blue) from the 3.6-Å (PA[63])[7] structure, as viewed
from the bottom. The domain 2 insertion loop (red) projects out
to bind the neighboring monomer in a groove between domains 2
and 4. (d) The domain 2 insertion loop contacts domain 4 from
its own monomer (residues 600-602) and domains 2 (residue 414)
and 4 (residues 668-670) from the neighboring monomer. N306 was
mutated to cysteine and labeled with pyrene for the experiments
described in Fig. 3b. Residues F313 and F314 are predicted to
form the tip of the membrane inserted  -hairpin (10).
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