Details

Autor(en) / Beteiligte

• Peters, Britta
• Stein, Johanna
• Klingl, Stefan
• Sander, Nathalie
• Sandmann, Achim
• Taccardi, Nicola
• Sticht, Heinrich
• Gerlach, Roman G
• Muller, Yves A
• Hensel, Michael

Titel

Structural and functional dissection reveals distinct roles of Ca.sup.2+-binding sites in the giant adhesin SiiE of Salmonella enterica

Ist Teil von

• PLoS pathogens, 2017-05, Vol.13 (5)

Ort / Verlag

Public Library of Science

Erscheinungsjahr

2017

Quelle

EZB-FREE-00999 freely available EZB journals

Beschreibungen/Notizen

• The giant non-fimbrial adhesin SiiE of Salmonella enterica mediates the first contact to the apical site of epithelial cells and enables subsequent invasion. SiiE is a 595 kDa protein composed of 53 repetitive bacterial immunoglobulin (BIg) domains and the only known substrate of the SPI4-encoded type 1 secretion system (T1SS). The crystal structure of BIg50-52 of SiiE revealed two distinct Ca.sup.2+ -binding sites per BIg domain formed by conserved aspartate or glutamate residues. In a mutational analysis Ca.sup.2+ -binding sites were disrupted by aspartate to serine exchange at various positions in the BIg domains of SiiE. Amounts of secreted SiiE diminish with a decreasing number of intact Ca.sup.2+ -binding sites. BIg domains of SiiE contain distinct Ca.sup.2+ -binding sites, with type I sites being similar to other T1SS-secreted proteins and type II sites newly identified in SiiE. We functionally and structurally dissected the roles of type I and type II Ca.sup.2+ -binding sites in SiiE, as well as the importance of Ca.sup.2+ -binding sites in various positions of SiiE. Type I Ca.sup.2+ -binding sites were critical for efficient secretion of SiiE and a decreasing number of type I sites correlated with reduced secretion. Type II sites were less important for secretion, stability and surface expression of SiiE, however integrity of type II sites in the C-terminal portion was required for the function of SiiE in mediating adhesion and invasion.