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Molecules 2015, 20(1), 1134-1150;

The Giant Adhesin SiiE of Salmonella enterica

Abteilung Mikrobiologie, Fachbereich Biologie/Chemie, Universität Osnabrück, Barbarastr. 11, Osnabrück 49076, Germany
Author to whom correspondence should be addressed.
Academic Editor: Tzi Bun NG
Received: 16 November 2014 / Accepted: 4 January 2015 / Published: 12 January 2015
(This article belongs to the Special Issue Lectins)
Full-Text   |   PDF [5784 KB, uploaded 12 January 2015]   |  


Salmonella enterica is a Gram-negative, food-borne pathogen, which colonizes the intestinal tract and invades enterocytes. Invasion of polarized cells depends on the SPI1-encoded type III secretion system (T3SS) and the SPI4-encoded type I secretion system (T1SS). The substrate of this T1SS is the non-fimbrial giant adhesin SiiE. With a size of 595 kDa, SiiE is the largest protein of the Salmonella proteome and consists of 53 repetitive bacterial immunoglobulin (BIg) domains, each containing several conserved residues. As known for other T1SS substrates, such as E. coli HlyA, Ca2+ ions bound by conserved D residues within the BIg domains stabilize the protein and facilitate secretion. The adhesin SiiE mediates the first contact to the host cell and thereby positions the SPI1-T3SS to initiate the translocation of a cocktail of effector proteins. This leads to actin remodeling, membrane ruffle formation and bacterial internalization. SiiE binds to host cell apical membranes in a lectin-like manner. GlcNAc and α2–3 linked sialic acid-containing structures are ligands of SiiE. Since SiiE shows repetitive domain architecture, we propose a zipper-like binding mediated by each individual BIg domain. In this review, we discuss the characteristics of the SPI4-T1SS and the giant adhesin SiiE. View Full-Text
Keywords: SiiE; bacterial IG domain; non-fimbrial adhesin; type I secretion system; lectin-like adhesin SiiE; bacterial IG domain; non-fimbrial adhesin; type I secretion system; lectin-like adhesin

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Barlag, B.; Hensel, M. The Giant Adhesin SiiE of Salmonella enterica. Molecules 2015, 20, 1134-1150.

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