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.
Katayama
Hiroo
H
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.
Janowiak
Blythe E
BE
Brzozowski
Marek
M
Juryck
Jordan
J
Falke
Scott
S
Gogol
Edward P
EP
Collier
R John
RJ
Fisher
Mark T
MT
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