title: Mechanistic insights into the inhibition of Sec61-dependent co- and post-translational translocation by mycolactone.
abstract: The virulence factor mycolactone is responsible for the immunosuppression and tissue necrosis that characterise Buruli ulcer, a disease caused by infection with Mycobacterium ulcerans In this study, we confirm that Sec61, the protein-conducting channel that coordinates entry of secretory proteins into the endoplasmic reticulum, is a primary target of mycolactone, and characterise the nature of its inhibitory effect. We conclude that mycolactone constrains the ribosome-nascent-chain-Sec61 complex, consistent with its broad-ranging perturbation of the co-translational translocation of classical secretory proteins. In contrast, the effect of mycolactone on the post-translational ribosome-independent translocation of short secretory proteins through the Sec61 complex is dependent on both signal sequence hydrophobicity and the translocation competence of the mature domain. Changes to protease sensitivity strongly suggest that mycolactone acts by inducing a conformational change in the pore-forming Sec61α subunit. These findings establish that mycolactone inhibits Sec61-mediated protein translocation and highlight differences between the co- and post-translational routes that the Sec61 complex mediates. We propose that mycolactone also provides a useful tool for further delineating the molecular mechanisms of Sec61-dependent protein translocation.
authors: Faculty of Life Sciences, University of Manchester, Michael Smith Building, Manchester M13 9PT, UK.
authors: Michael
authors: M
authors: McKenna
authors: Department of Microbial Sciences, School of Bioscience and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK.
authors: Rachel E
authors: RE
authors: Simmonds
authors: Faculty of Life Sciences, University of Manchester, Michael Smith Building, Manchester M13 9PT, UK stephen.high@manchester.ac.uk.
authors: Stephen
authors: S
authors: High
mesh_terms: D000818:Animals; D054312:Buruli Ulcer / Q000473:pathology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D018942:Macrolides / Q000378:metabolism*; D019911:Mycobacterium ulcerans / Q000472:pathogenicity*; D021381:Protein Transport / Q000502:physiology; D012270:Ribosomes / Q000378:metabolism; D000069816:SEC Translocation Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism*
chemical_list: D018942:Macrolides; D000069816:SEC Translocation Channels; C117218:mycolactone
keywords: Buruli ulcer; Endoplasmic reticulum; Mycobacterium ulcerans; Mycolactone; Sec61; Short secretory protein