GroEL as a molecular scaffold for structural analysis of the anthrax toxin pore.
We analyzed the 440-kDa transmembrane pore formed by the protective antigen (PA) moiety of anthrax toxin in the presence of GroEL by negative-stain electron microscopy. GroEL binds both the heptameric PA prepore and the PA pore. The latter interaction retards aggregation of the pore, prolonging its insertion-competent state. Two populations of unaggregated pores were visible: GroEL-bound pores and unbound pores. This allowed two virtually identical structures to be reconstructed, at 25-A and 28-A resolution, respectively. The structures were mushroom-shaped objects with a 125-A-diameter cap and a 100-A-long stem, consistent with earlier biochemical data. Thus, GroEL provides a platform for obtaining initial glimpses of a membrane protein structure in the absence of lipids or detergents and can function as a scaffold for higher-resolution structural analysis of the PA pore.
Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas Life Sciences Innovation Center Building, Kansas City, Kansas 66160, USA.
Hiroo
H
Katayama
Blythe E
BE
Janowiak
Marek
M
Brzozowski
Jordan
J
Juryck
Scott
S
Falke
Edward P
EP
Gogol
R John
RJ
Collier
Mark T
MT
Fisher
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000648:ultrastructure; D001427:Bacterial Toxins / Q000737:chemistry*; D018834:Chaperonin 60 / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D018360:Crystallography, X-Ray; D008854:Microscopy, Electron; D008958:Models, Molecular; D011485:Protein Binding / Q000187:drug effects
D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D018834:Chaperonin 60; C030325:anthrax toxin; D000255:Adenosine Triphosphate