Latching onto fibrinogen

A bacterial adhesin grabs hold of its extracellular matrix target, then covers it and latches the compartment shut, according to two structures determined by Karthe Ponnuraj, Sthanam Narayan (University of Alabama, Birmingham, AL), Magnus Hook (Texas A&M, Houston, TX), and colleagues.

The first structure, of the unbound SdrG protein from Staphylococcus epidermis, shows a wide cleft between two immunoglobulin-like domains. This cleft is the binding site for a peptide from the extracellular matrix protein fibrinogen.

But this is no simple binding event. The presence of the peptide, found the researchers, induces conformational changes in a COOH- terminal region of SdrG that previously extended out from the protein's N3 domain to wave in the wind. After peptide binding, the region now extends over the peptide, thus forming a...