Molecular interfaces of the galactose-binding protein tectonin domains in host-pathogen interaction

Diana Hooi Ping Low, Vladimir Frecer, Agnès Le Saux, Ganesh Anand Srinivasan, Bow Ho, Jianzhu Chen, Jeak Ling Ding

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

β-Propeller proteins function in catalysis, protein-protein interaction, cell cycle regulation, and innate immunity. The galactose-binding protein (GBP) from the plasma of the horse-shoe crab, Carcinoscorpius rotundicauda, is a β-propeller protein that functions in antimicrobial defense. Studies have shown that upon binding to Gram-negative bacterial lipopolysaccharide (LPS), GBP interacts with C-reactive protein (CRP) to form a pathogen-recognition complex, which helps to eliminate invading microbes. However, the molecular basis of interactions between GBP and LPS and how it interplays with CRP remain largely unknown. By homology modeling, we showed that GBP contains six β-propeller/Tectonin domains. Ligand docking indicated that Tectonin domains 6 to 1 likely contain the LPS binding sites. Protein-protein interaction studies demonstrated that Tectonin domain 4 interacts most strongly with CRP. Hydrogen-deuterium exchange mass spectrometry mapped distinct sites of GBP that interact with LPS and with CRP, consistent with in silico predictions. Furthermore, infection condition (lowered Ca 2+ level) increases GBP-CRP affinity by 1000-fold. Resupplementing the system with a physiological level of Ca2+ did not reverse the protein-protein affinity to the basal state, suggesting that the infection-induced complex had undergone irreversible conformational change. We propose that GBP serves as a bridging molecule, participating in molecular interactions, GBP-LPS and GBP-CRP, to form a stable pathogen-recognition complex. The interaction interfaces in these two partners suggest that Tectonin domains can differentiate self/nonself, crucial to frontline defense against infection. In addition, GBP shares architectural and functional homologies to a human protein, hTectonin, suggesting its evolutionarily conservation for ∼500 million years, from horseshoe crab to human.

Original languageEnglish (US)
Pages (from-to)9898-9907
Number of pages10
JournalJournal of Biological Chemistry
Volume285
Issue number13
DOIs
StatePublished - Mar 26 2010

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Fingerprint Dive into the research topics of 'Molecular interfaces of the galactose-binding protein tectonin domains in host-pathogen interaction'. Together they form a unique fingerprint.

Cite this