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© The Rockefeller University Press, 0021-9525/2003/11/435 $8.00
The Journal of Cell Biology, Volume 163, Number 3, 435-435

Latching onto fibrinogen

Fibrinogen (purple) is latched in place when the G" strand crosses from N3 (yellow) to N2 (green). Narayana/Elsevier

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 hydrogen-bonded roof, and then inserts into a ß-sheet in the adjacent N2 domain.

The latch may be far from unique. The region in N2 that receives the latching ß strand makes up a motif that is present in many other gram-positive bacterial adhesins. These proteins, which are used by bacteria that replicate extracellularly, "are all like extending velcros," says Narayan, "but there is specificity." For SdrG, the binding also covers the thrombin-cleavage site in fibrinogen. This prevents the formation of fibrinopeptides that can act as chemoattractants for leukocytes and fibroblasts.

Reference:

Ponnuraj, K., et al. 2003. Cell. 115:217–228.[CrossRef][Medline]

William A. Wells

wellsw{at}rockefeller.edu

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This Article Full Text (PDF, 691K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Wells, W. A. Search for Related Content PubMed Articles by Wells, W. A. Social Bookmarking                            What's this?