부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jmb.2008.01.053 Byline: Robin M. Delahay (1)(2), Graham D. Balkwill (3), Karen A. Bunting (4), Wayne Edwards (3), John C. Atherton (1)(2), Mark S. Searle (3) Keywords: Helicobacter pylori; CagY; tetratricopeptide repeat; [alpha]-helical repeat; type IV secretion Abbreviations: T4SS, type IV secretion system; PAI, pathogenicity island; TPR, tetratricopeptide repeat; PBS, phosphate-buffered saline Abstract: The cag-pathogenicity-island-encoded type IV secretion system of Helicobacter pylori functions to translocate the effector protein CagA directly through the plasma membrane of gastric epithelial cells. Similar to other secretion systems, the Cag type IV secretion system elaborates a surface filament structure, which is unusually sheathed by the large cag-pathogenicity-island-encoded protein CagY. CagY is distinguished by unusual amino acid composition and extensive repetitive sequence organised into two defined repeat regions. The second and major repeat region (CagY.sub.rpt2) has a regular disposition of six repetitive motifs, which are subject to deletion and duplication, facilitating the generation of CagY size and phenotypic variants. In this study, we show CagY.sub.rpt2 to comprise two highly thermostable and acid-stable [alpha]-helical structural motifs, the most abundant of which (motif A) occurs in tandem arrays of one to six repeats terminally flanked by single copies of the second repeat (motif B). Isolated motifs demonstrate hetero- and homomeric interactions, suggesting a propensity for uniform assembly of discrete structural subunit motifs within the larger CagY.sub.rpt2 structure. Consistent with this, CagY proteins comprising substantially different repeat 2 motif organisations demonstrate equivalent CagA translocation competence, illustrating a remarkable structural and functional tolerance for precise deletion and duplication of motif subunits. We provide the first insight into the structural basis for CagY.sub.rpt2 assembly that accommodates both the variable motif sequence composition and the extensive contraction/expansion of repeat modules within the CagY.sub.rpt2 region. Author Affiliation: (1) Institute of Infection, Immunity and Inflammation, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK (2) Wolfson Digestive Diseases Centre, University of Nottingham, C Floor, South Block, Queen's Medical Centre, Nottingham NG7 2UH, UK (3) School of Chemistry, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK (4) Institute of Genetics, Queen's Medical Centre, University of Nottingham, Nottingham NG7 2UH, UK Article History: Received 13 December 2007; Revised 18 January 2008; Accepted 18 January 2008 Article Note: (miscellaneous) Edited by M. Gottesman