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Structure of anthrax lethal toxin prepore complex suggests a pathway for efficient cell entry

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ABSTRACT

Anthrax toxin is a tripartite complex in which the protective antigen moiety forms a pore through which lethal factor and edema factor are translocated. Fabre et al. reveal a mechanism for efficient translocation in their structure of the heptameric protective antigen prepore bound to three lethal factors.

No MeSH data available.


Related in: MedlinePlus

LF head to tail interactions in (PA63)7–(LF)3. (A) The C-terminal domain of LF (1LFC) establishes a large contact with the N-domain of the adjacent LF molecule (2LFN). This interaction (blue circle) is shown in the EM map displayed at two different contour levels (131,000 A3 and 112,000 A3 in A and B, respectively). Two adjacent LFC domains establish a minor interaction (marked by a green arrow) that is broken at the higher threshold (see B). A very similar interaction is observed between 2LFC and 3LFN. (B) Close-up with two atomic models of LF fit into the density. The top of the PA63 heptamer (shown in red) is just visible. The blue circle highlights the novel 1LFC–2LFN interaction with coloration in orange of segments 572–579 of 1LFC and 75–83 of 2LFN. This region is identical in our model for 2LFC–3LFN. The black arrow highlights the position of the α1–β1 segment of 2LFN, which has been modeled in the open conformation (similar to the conformation solved by x-ray crystallography for (PA63)8–(LFN)4 reported in Feld et al. [2010]) and is an identical position for 1LFN and 3LFN.
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fig5: LF head to tail interactions in (PA63)7–(LF)3. (A) The C-terminal domain of LF (1LFC) establishes a large contact with the N-domain of the adjacent LF molecule (2LFN). This interaction (blue circle) is shown in the EM map displayed at two different contour levels (131,000 A3 and 112,000 A3 in A and B, respectively). Two adjacent LFC domains establish a minor interaction (marked by a green arrow) that is broken at the higher threshold (see B). A very similar interaction is observed between 2LFC and 3LFN. (B) Close-up with two atomic models of LF fit into the density. The top of the PA63 heptamer (shown in red) is just visible. The blue circle highlights the novel 1LFC–2LFN interaction with coloration in orange of segments 572–579 of 1LFC and 75–83 of 2LFN. This region is identical in our model for 2LFC–3LFN. The black arrow highlights the position of the α1–β1 segment of 2LFN, which has been modeled in the open conformation (similar to the conformation solved by x-ray crystallography for (PA63)8–(LFN)4 reported in Feld et al. [2010]) and is an identical position for 1LFN and 3LFN.

Mentions: Our rigid-body docking demonstrated that the packing between LFN and PA63 is nearly identical to that observed in the crystal structure of LFN bound to the octameric prepore (Feld et al., 2010). In the octamer complex (Feld et al., 2010), however, there is refolding of a short N-terminal α1–β1 segment (residues 29–51) of LFN, compared with the solution structure of LF (Pannifer et al., 2001), in which the β1 strand peels away from the end of its sheet, enabling helix α1 to swing around and insert into a pocket on the inner rim of the prepore (this has been called the open conformation). We found that this open conformation fitted significantly better into our EM map than the closed conformation (confidence level of 0.9995) for all three LF molecules. We therefore rebuilt these residues to generate our final model as described in detail in Materials and methods. We note that this revised model eliminates steric clashes with LFC predicted by our initial rigid-body model but does not eliminate contacts between LFC (a C-terminal helix/loop, residues 573–583) and the N-terminal sheet of LFN of its counterclockwise neighbor, as indicated by the strong intermolecular density noted above (Figs. 4 B and 5).


Structure of anthrax lethal toxin prepore complex suggests a pathway for efficient cell entry
LF head to tail interactions in (PA63)7–(LF)3. (A) The C-terminal domain of LF (1LFC) establishes a large contact with the N-domain of the adjacent LF molecule (2LFN). This interaction (blue circle) is shown in the EM map displayed at two different contour levels (131,000 A3 and 112,000 A3 in A and B, respectively). Two adjacent LFC domains establish a minor interaction (marked by a green arrow) that is broken at the higher threshold (see B). A very similar interaction is observed between 2LFC and 3LFN. (B) Close-up with two atomic models of LF fit into the density. The top of the PA63 heptamer (shown in red) is just visible. The blue circle highlights the novel 1LFC–2LFN interaction with coloration in orange of segments 572–579 of 1LFC and 75–83 of 2LFN. This region is identical in our model for 2LFC–3LFN. The black arrow highlights the position of the α1–β1 segment of 2LFN, which has been modeled in the open conformation (similar to the conformation solved by x-ray crystallography for (PA63)8–(LFN)4 reported in Feld et al. [2010]) and is an identical position for 1LFN and 3LFN.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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fig5: LF head to tail interactions in (PA63)7–(LF)3. (A) The C-terminal domain of LF (1LFC) establishes a large contact with the N-domain of the adjacent LF molecule (2LFN). This interaction (blue circle) is shown in the EM map displayed at two different contour levels (131,000 A3 and 112,000 A3 in A and B, respectively). Two adjacent LFC domains establish a minor interaction (marked by a green arrow) that is broken at the higher threshold (see B). A very similar interaction is observed between 2LFC and 3LFN. (B) Close-up with two atomic models of LF fit into the density. The top of the PA63 heptamer (shown in red) is just visible. The blue circle highlights the novel 1LFC–2LFN interaction with coloration in orange of segments 572–579 of 1LFC and 75–83 of 2LFN. This region is identical in our model for 2LFC–3LFN. The black arrow highlights the position of the α1–β1 segment of 2LFN, which has been modeled in the open conformation (similar to the conformation solved by x-ray crystallography for (PA63)8–(LFN)4 reported in Feld et al. [2010]) and is an identical position for 1LFN and 3LFN.
Mentions: Our rigid-body docking demonstrated that the packing between LFN and PA63 is nearly identical to that observed in the crystal structure of LFN bound to the octameric prepore (Feld et al., 2010). In the octamer complex (Feld et al., 2010), however, there is refolding of a short N-terminal α1–β1 segment (residues 29–51) of LFN, compared with the solution structure of LF (Pannifer et al., 2001), in which the β1 strand peels away from the end of its sheet, enabling helix α1 to swing around and insert into a pocket on the inner rim of the prepore (this has been called the open conformation). We found that this open conformation fitted significantly better into our EM map than the closed conformation (confidence level of 0.9995) for all three LF molecules. We therefore rebuilt these residues to generate our final model as described in detail in Materials and methods. We note that this revised model eliminates steric clashes with LFC predicted by our initial rigid-body model but does not eliminate contacts between LFC (a C-terminal helix/loop, residues 573–583) and the N-terminal sheet of LFN of its counterclockwise neighbor, as indicated by the strong intermolecular density noted above (Figs. 4 B and 5).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Anthrax toxin is a tripartite complex in which the protective antigen moiety forms a pore through which lethal factor and edema factor are translocated. Fabre et al. reveal a mechanism for efficient translocation in their structure of the heptameric protective antigen prepore bound to three lethal factors.

No MeSH data available.


Related in: MedlinePlus