Of linkers and autochaperones: an unambiguous nomenclature to identify common and uncommon themes for autotransporter secretion |
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| Authors: | Igor Drobnak Esther Braselmann Julie L Chaney Denisse L Leyton Harris D Bernstein Trevor Lithgow Joen Luirink James P Nataro Patricia L Clark |
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| Institution: | 1. Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA;2. Research School of Biology, Australian National University, Canberra, ACT, Australia;3. Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA;4. Department of Microbiology, Monash University, Melbourne, Vic., Australia;5. Section of Molecular Microbiology, Department of Molecular Cell Biology, VU University, Amsterdam, The Netherlands;6. Abera Bioscience AB, Stockholm, Sweden;7. Department of Pediatrics, University of Virginia School of Medicine and University of Virginia Children's Hospital, Charlottesville, VA, USA |
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| Abstract: | Autotransporter (AT) proteins provide a diverse array of important virulence functions to Gram‐negative bacterial pathogens, and have also been adapted for protein surface display applications. The ‘autotransporter’ moniker refers to early models that depicted these proteins facilitating their own translocation across the bacterial outer membrane. Although translocation is less autonomous than originally proposed, AT protein segments upstream of the C‐terminal transmembrane β‐barrel have nevertheless consistently been found to contribute to efficient translocation and/or folding of the N‐terminal virulence region (the ‘passenger’). However, defining the precise secretion functions of these AT regions has been complicated by the use of multiple overlapping and ambiguous terms to define AT sequence, structural, and functional features, including ‘autochaperone’, ‘linker’ and ‘junction’. Moreover, the precise definitions and boundaries of these features vary among ATs and even among research groups, leading to an overall murky picture of the contributions of specific features to translocation. Here we propose a unified, unambiguous nomenclature for AT structural, functional and conserved sequence features, based on explicit criteria. Applied to 16 well‐studied AT proteins, this nomenclature reveals new commonalities for translocation but also highlights that the autochaperone function is less closely associated with a conserved sequence element than previously believed. |
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