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Biochim Biophys Acta Gen Subj. 2017 Jan;1861(1 Pt A):3490-3497. doi: 10.1016/j.bbagen.2016.09.015. Epub 2016 Sep 15.

Interaction of an esophageal MEG protein from schistosomes with a human S100 protein involved in inflammatory response.

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Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil.
Núcleo de Enteroparasitas, Centro de Parasitologia e Micologia, Instituto Adolfo Lutz, São Paulo, Brazil.
Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
Institute of Structural and Molecular Biology, Birkbeck College, University of London, London, U.K.
Instituto de Química, Universidade de São Paulo, São Paulo, Brazil; Instituto Butantan, São Paulo, SP, Brazil.
Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil. Electronic address:



The Micro-Exon Gene-14 (MEG-14) displays a remarkable structure that allows the generation of antigenic variation in Schistosomes. Previous studies showed that the soluble portion of the MEG-14 protein displays features of an intrinsically disordered protein and is expressed exclusively in the parasite esophageal gland. These features indicated a potential for interaction with host proteins present in the plasma and cells from ingested blood.


A yeast two-hybrid experiment using as bait the soluble domain of Schistosoma mansoni MEG-14 (sMEG-14) against a human leukocyte cDNA library was performed. Pull-down and surface plasmon resonance (SPR) experiments were used to validate the interaction between sMEG-14 and human S100A9. Synchrotron radiation circular dichroism (SRCD) were used to detect structural changes upon interaction between sMEG-14 and human S100A9. Feeding of live parasites with S100A9 attached to a fluorophore allowed the tracking of the fate of this protein in the parasite digestive system.


S100A9 interacted with sMEG-14 consistently in yeast two-hybrid assay, pull-down and SPR experiments. SRCD suggested that MEG-14 acquired a more regular structure as a result of the interaction with S100A9. Accumulation of recombinant S100A9 in the parasite's esophageal gland, when ingested by live worms suggests that such interaction may occur in vivo.


S100A9, a protein previously described to be involved in modulation of inflammatory response, was found to interact with sMEG-14.


Our results allow proposing a mechanism involving MEG-14 for the parasite to block inflammatory signaling, which would occur upon release of S100A9 when ingested blood cells are lysed.


Intrinsically disordered proteins; Micro-exon gene; Protein-protein interaction; Synchrotron radiation circular dichroism spectroscopy

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