3mhz | pdb_00003mhz
1.7A structure of 2-fluorohistidine labeled Protective Antigen
Structural highlights
FunctionPAG_BACAN One of the three proteins composing the anthrax toxin, the agent which infects many mammalian species and that may cause death. PA binds to a receptor (ATR) in sensitive eukaryotic cells, thereby facilitating the translocation of the enzymatic toxin components, edema factor and lethal factor, across the target cell membrane. PA associated with LF causes death when injected, PA associated with EF produces edema. PA induces immunity to infection with anthrax. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe protective antigen (PA) component of the anthrax toxin forms pores within the low pH environment of host endosomes through mechanisms that are poorly understood. It has been proposed that pore formation is dependent on histidine protonation. In previous work, we biosynthetically incorporated 2-fluorohistidine (2-FHis), an isosteric analogue of histidine with a significantly reduced pK(a) ( approximately 1), into PA and showed that the pH-dependent conversion from the soluble prepore to a pore was unchanged. However, we also observed that 2-FHisPA was nonfunctional in the ability to mediate cytotoxicity of CHO-K1 cells by LF(N)-DTA and was defective in translocation through planar lipid bilayers. Here, we show that the defect in cytotoxicity is due to both a defect in translocation and, when bound to the host cellular receptor, an inability to undergo low pH-induced pore formation. Combining X-ray crystallography with hydrogen-deuterium (H-D) exchange mass spectrometry, our studies lead to a model in which hydrogen bonds to the histidine ring are strengthened by receptor binding. The combination of both fluorination and receptor binding is sufficient to block low pH-induced pore formation. Evidence that histidine protonation of receptor-bound anthrax protective antigen is a trigger for pore formation.,Wimalasena DS, Janowiak BE, Lovell S, Miyagi M, Sun J, Zhou H, Hajduch J, Pooput C, Kirk KL, Battaile KP, Bann JG Biochemistry. 2010 Aug 24;49(33):6973-83. PMID:20672855[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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