Anthrax toxin complexes: heptameric protective antigen can bind lethal factor and edema factor simultaneously |
| |
Authors: | Pimental Ruth-Anne L Christensen Kenneth A Krantz Bryan A Collier R John |
| |
Institution: | Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA. |
| |
Abstract: | The 83 kDa protective antigen (PA(83)) component of anthrax toxin, after proteolytic activation, self-associates to form ring-shaped heptamers (PA(63)](7)) that bind and aid delivery of the Edema Factor (EF) and Lethal Factor (LF) components to the cytosol. Here we show using fluorescence (F?rster) resonance energy transfer that a molecule of PA(63)](7) can bind EF and LF simultaneously. We labeled EF and LF with an appropriate donor/acceptor pair and found quenching of the donor and an increase in sensitized emission of the acceptor when, and only when, a mixture of the labeled proteins was combined with PA(63)](7). Addition of unlabeled PA(63)-binding domain of LF to the mixture competitively displaced labeled EF and LF, causing a loss of energy transfer. In view of the known maximum occupancy of 3 ligand molecules per PA(63)](7), these findings indicate that PA, EF, and LF can form mixtures of liganded toxin complexes containing both EF and LF. |
| |
Keywords: | Anthrax toxin Edema factor Lethal factor Protective antigen Stoichiometry Ligand binding Macromolecular interactions |
本文献已被 ScienceDirect PubMed 等数据库收录! |
|