Title
Direct detection of membrane-inserting fragments defines the translocation pores of a family of pathogenic toxins
Author
Kathleen E. Orrell, Åsa Tellgren-Roth, Mercedes Di Bernardo, Zhifen Zhang, Flavia Cuviello, Jasmin Lundqvist, Gunnarvon Heijne, IngMarie Nilsson, Roman A. Melnyk
Year
2018
Journal
Journal of Molecular Biology
Abstract
Large Clostridial Toxins (LCTs) are a family of homologous proteins toxins that are directly responsible for the symptoms associated with a number of Clostridial infections that cause disease in humans and in other animals. LCTs damage tissues by delivering a glucosyltransferase domain, which inactivates small GTPases, across the endosomal membrane and into the cytosol of target cells. Elucidating the mechanism of translocation for LCTs has been hampered by difficulties associated with identifying marginally hydrophobic segments that insert into the bounding membrane to form the translocation pore. Here, we directly measured the membrane-insertion partitioning propensity for segments spanning the putative pore-forming region using a translocon-mediated insertion assay and synthetic peptides. We identified membrane-inserting segments, as well as a conserved and functionally important negatively charged residue that requires protonation for efficient membrane insertion. We provide a model of the LCT pore, which provides insights into translocation for this enigmatic family of α-helical translocases.
Instrument
J-810
Keywords
Circular dichroism, Secondary structure, Membrane interactions, Biochemistry