Premium
The immune evasion protein Sbi of Staphylococcus aureus occurs both extracellularly and anchored to the cell envelope by binding lipoteichoic acid
Author(s) -
Smith Emma Jane,
Corrigan Rebecca M.,
van der Sluis Tetje,
Gründling Angelika,
Speziale Pietro,
Geoghegan Joan A.,
Foster Timothy J.
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2011.07966.x
Subject(s) - lipoteichoic acid , biology , cell envelope , staphylococcus aureus , teichoic acid , cytoplasm , cell fractionation , cell membrane , biochemistry , membrane , bacteria , protein a , cell wall , membrane protein , microbiology and biotechnology , escherichia coli , antibody , gene , immunology , genetics
Summary The Sbi protein of Staphylococcus aureus comprises two IgG‐binding domains similar to those of protein A and a region that triggers the activation of complement C3. Sbi is expressed on the cell surface but its C‐terminal domain lacks motifs associated with wall or membrane anchoring of proteins in Gram‐positive bacteria. Cell‐associated Sbi fractionates with the cytoplasmic membrane and is not solubilized during protoplast formation. S. aureus expressing Sbi truncates of the C‐terminal Y domain allowed identification of residues that are required for association of Sbi with the membrane. Recombinant Sbi bound to purified cytoplasmic membrane material in vitro and to purified lipoteichoic acid. This explains how Sbi partitions with the membrane in fractionation experiments yet is partially exposed on the cell surface. An LTA‐defective mutant of S. aureus had reduced levels of Sbi in the cytoplasmic membrane.