Lars Frykberg | PubMed Health

PubMed1999

Staphylococcus aureus expresses a cell surface protein that binds both IgG and beta2-glycoprotein I.

The existence of a second IgG-binding protein, protein Sbi, in Staphylococcus aureus has been reported previously. Later data indicated that protein Sbi also bound another serum component. This component has now been affinity-purified on immobilized protein Sbi and identified as beta2-glycoprotein I (beta2-GPI), also known as apolipoprotein H. The minimal beta2-GPI-binding domain was identified by shotgun phage display and the binding was shown to be mediated by a region of 57 amino acids, clearly separated from the IgG-binding domain. It is also shown that protein Sbi, and thus the beta2-GPI-binding activity, is expressed on the staphylococcal cell surface at levels varying between strains.

Amino Acid Sequence↗

PubMed1998

A second IgG-binding protein in Staphylococcus aureus.

Most strains of Staphylococcus aureus express IgG-binding activity and this binding has been considered to be solely mediated by protein A. However, the existence of a second gene in S. aureus strain 8325-4 encoding an IgG-binding polypeptide was recently reported. This novel IgG-binding polypeptide was found after panning a shotgun phage display library, made from chromosomal DNA, against immobilized human IgG. The complete gene (sbi) encoding this novel IgG-binding protein, denoted protein Sbi, has now been cloned and sequenced. Analysis of other S. aureus strains showed that this gene is not unique for strain 8325-4. The protein consists of 436 amino acids and exhibits an immunoglobulin-binding specificity similar to protein A. Furthermore, it is shown that Sbi is highly expressed in strain Newman 4, which shows that IgG-binding activity in S. aureus can be mediated by proteins other than protein A.

Bacterial Outer Membrane Proteins↗