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Updated: Jul 7, 2026

Detecting and Characterizing Protein Self-Assembly In Vivo by Flow Cytometry
Published on: July 17, 2019
The macromolecular assembly of pathogen-recognition receptors is impelled by serine proteases, via their complement
Agnès Le Saux1, Patricia Miang Lon Ng, Joanne Jing Yun Koh
1Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore.
Abstract:
Although the innate immune response is triggered by the formation of a stable assembly of pathogen-recognition receptors (PRRs) onto the pathogens, the driving force that enables this PRR-PRR interaction is unknown. Here, we show that serine proteases, which are activated during infection, participate in associating with the PRRs. Inhibition of serine proteases gravely impairs the PRR assembly. Using yeast two-hybrid and pull-down methods, we found that two serine proteases in the horseshoe crab Carcinoscorpius rotundicauda are able to bind to the following three core members of PRRs: galactose-binding protein, Carcinolectin-5 and C-reactive protein. These two serine proteases are (1) Factor C, which activates the coagulation pathway, and (2) C2/Bf, a protein from the complement pathway. By systematic molecular dissection, we show that these serine proteases interact with the core "pathogen-recognition complex" via their complement control protein modules.
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