Protein translocation through the anthrax toxin transmembrane pore is driven by a proton gradient |
| |
Authors: | Krantz Bryan A Finkelstein Alan Collier R John |
| |
Institution: | Department of Microbiology and Molecular Genetics, Harvard Medical School 200 Longwood Ave, Boston, MA 02115, USA. |
| |
Abstract: | Protective antigen (PA) from anthrax toxin assembles into a homoheptamer on cell surfaces and forms complexes with the enzymatic components: lethal factor (LF) and edema factor (EF). Endocytic vesicles containing these complexes are acidified, causing the heptamer to transform into a transmembrane pore that chaperones the passage of unfolded LF and EF into the cytosol. We show in planar lipid bilayers that a physiologically relevant proton gradient (DeltapH, where the endosome is acidified relative to the cytosol) is a potent driving force for translocation of LF, EF and the LF amino-terminal domain (LFN) through the PA63 pore. DeltapH-driven translocation occurs even under a negligible membrane potential. We found that acidic endosomal conditions known to destabilize LFN correlate with an increased translocation rate. The hydrophobic heptad of lumen-facing Phe427 residues in PA (or phi clamp) drives translocation synergistically under a DeltapH. We propose that a Brownian ratchet mechanism proposed earlier for the phi clamp is cooperatively linked to a protonation-state, DeltapH-driven ratchet acting trans to the phi-clamp site. In a sense, the channel functions as a proton/protein symporter. |
| |
Keywords: | translocation proton gradient translocase protein unfolding planar bilayers |
本文献已被 ScienceDirect PubMed 等数据库收录! |
|