Understanding Periperal Membrane Protein Interactions | BPS Thematic Meeting

Understanding Peripheral Membrane Protein Interactions: Structure, Dynamics, Function and Therapy

Tuesday Speaker Abstracts

STRUCTURE AND MEMBRANE TRANSLOCATION PROCESS OF THE BORDETELLA PERTUSSIS CYAA TOXIN Alexandre Chenal ; 1 Institut Pasteur, Structural Biology & Chemistry, Paris, France The adenylate cyclase CyaA toxin (a 1706-residue RTX protein), is secreted by Bordetella pertussis, the causative agent of whooping cough. CyaA plays an essential role in the early stages of colonization of the human respiratory tract. However, the process of cell intoxication by CyaA is still poorly understood. Following its secretion by a type I secretion system, CyaA intoxicates human cells by directly translocating its catalytic domain (ACD) across the plasma membrane of target cells. We show that the CyaA translocation region exhibits the intrinsic propensity to translocate across the plasma membrane and to bind with high affinity to the endogenous calmodulin (CaM), favoring ACD translocation. ACD is then refolded in the cytoplasm upon CaM binding and catalyzes high levels of cAMP, leading to cell death. Moreover, high resolution structural characterization of CyaA has remained elusive due to its size, multi-domain organization, flexibility, and aggregation propensity. We have recently overcome these challenges by integrating a wide array of experimental data with advanced modelling techniques, resulting in the first structural ensembles of CyaA in solution. Our results illustrate how the structural flexibility of CyaA is crucial for its secretion, folding, translocation across the plasma membrane and intoxication of target cells. All these steps involve disorder-to-order conformational transitions that are finely tuned to the environmental conditions to which CyaA is exposed on its journey from the bacterium to the cytoplasm of the eukaryotic cell. These results open new opportunities for both basic research and biotechnological applications, where recombinant CyaA proteins are used as antigen delivery vehicles and as a potential protective antigen in the next generation of pertussis vaccines.

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