title: Single molecule atomic force microscopy of aerolysin pore complexes reveals unexpected star-shaped topography.
abstract: Aerolysin is the paradigmatic member of a large family of toxins that convert from a water-soluble monomer/dimer into a membrane-spanning oligomeric pore. While there is x-ray crystallographic data of its water-soluble conformation, the most recent structural model of the membrane-inserted pore is based primarily on data of water-soluble tetradecamers of mutant protein, together with computational modeling ultimately performed in vacuum. Here we examine this pore model with atomic force microscopy (AFM) of membrane-associated wild-type complexes and all-atom molecular dynamics (MD) simulations in water. In striking contrast to a disc-shaped cap region predicted by the present model, the AFM images reveal a star-shaped complex, with a central ring surrounded by seven radial projections. Further, the MD simulations suggest that the locations of the receptor-binding (D1) domains in the present model are not correct. However, a modified model in which the D1 domains, rather than localized at fixed positions, adopt a wide range of configurations through fluctuations of an intervening linker is compatible with existing data. Thus our work not only demonstrates the importance of directly resolving such complexes in their native environment but also points to a dynamic receptor binding region, which may be critical for toxin assembly on the cell surface.
authors.affiliation: Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: He
authors.affiliation: Key Laboratory of Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Jiabin
authors.initials: J
authors.lastname: Wang
authors.affiliation: Division of Physical Biology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.affiliation: Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.|Key Laboratory of Systems Biomedicine, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Jielin
authors.initials: J
authors.lastname: Sun
authors.affiliation: Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Daniel Mark
authors.initials: DM
authors.lastname: Czajkowsky
authors.affiliation: Bio-ID Center, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Shao
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D018625:Microscopy, Atomic Force / Q000379:methods*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D000072760:Single Molecule Imaging / Q000379:methods*
chemical_list: D001427:Bacterial Toxins; D052899:Pore Forming Cytotoxic Proteins; C032676:aerolysin
keywords: aerolysin; atomic force microscopy; pore-forming proteins