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Structure formed by strep protein can trigger toxic shock

Date:
May 27, 2011
Source:
University of California - San Diego
Summary:
Strep can turn deadly when a protein found on its surface triggers a widespread inflammatory reaction. The protein links with a host protein that is normally involved in blood clotting to form scaffolds. These assemble into dense superstructures that immune cells mistake for blood clots and overreact, leading to sepsis, shock, organ failure and death.

M1 joints (red) and fibrinogen struts (green) form a scaffold. Dense assemblies trigger a pathological response that can lead to toxic shock.
Credit: Partho Ghosh lab/UC San Diego

Infection with some strains of strep turn deadly when a protein found on their surface triggers a widespread inflammatory reaction. In a report published April 7 in the journal Nature, researchers describe the precise architecture of a superstructure formed when the bacterial protein called M1 links with a host protein, fibrinogen, that is normally involved in clotting blood.

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The proteins form scaffolds with M1 joints and fibrinogen struts that assemble into dense superstructures. Frontline immune cells called neutrophils mistake these thick networks for blood clots and overreact, releasing a chemical signal that can dilate vessels to the point where they leak, the team reports.

"We knew that M1 plus fibrinogen was inflammatory, but how was unknown. By determining the structure of this complex, we were able to identify the characteristics that lead to a sepsis response," said Partho Ghosh, Ph.D., professor of chemistry and biochemistry at the University of California, San Diego who studies the structure of virulence factors and led this project.

Ghosh and colleagues found that the density of the M1-fibrinogen structure was a critical characteristic. Looser structures or separate fibers formed by altered versions of M1 failed to trigger a pathological response.

"This research provides the first snapshot of the interaction between this key bacterial virulence factor and its human target at the atomic level," said Victor Nizet, M.D., professor of pediatrics and pharmacy and a co-author of the report.

Difficult to treat once they set in, the leaking blood vessels and organ failure of strep-induced toxic shock prove fatal for 30 percent of patients. Ghosh and Nizet have a long-standing collaboration aimed at designing treatments to counteract the toxic effects of strep protein.

Additional co-authors include Pauline Macheboeuf and Cosmo Buffalo of the department of chemistry and biochemistry, Annelies Zinkernagel and Jason Cole of the department of pediatrics, and Chi-yu Fu and Jack Johnson of The Scripps Research Institute. The National Institutes of Health funded this work.


Story Source:

The above story is based on materials provided by University of California - San Diego. Note: Materials may be edited for content and length.


Journal Reference:

  1. Pauline Macheboeuf, Cosmo Buffalo, Chi-yu Fu, Annelies S. Zinkernagel, Jason N. Cole, John E. Johnson, Victor Nizet, Partho Ghosh. Streptococcal M1 protein constructs a pathological host fibrinogen network. Nature, 2011; 472 (7341): 64 DOI: 10.1038/nature09967

Cite This Page:

University of California - San Diego. "Structure formed by strep protein can trigger toxic shock." ScienceDaily. ScienceDaily, 27 May 2011. <www.sciencedaily.com/releases/2011/04/110406131800.htm>.
University of California - San Diego. (2011, May 27). Structure formed by strep protein can trigger toxic shock. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2011/04/110406131800.htm
University of California - San Diego. "Structure formed by strep protein can trigger toxic shock." ScienceDaily. www.sciencedaily.com/releases/2011/04/110406131800.htm (accessed December 21, 2014).

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