Study of structure and protein partners of proteins coded by micro-exon genes of Schistosoma mansoni

Author(s)

Débora Orcia

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2015-05-15

Examining board members

Ricardo De Marco; Maria Cristina Nonato Costa; Marcelo Rosado Fantappié; Leonardo Paiva Farias; Luciana Cezar de Cerqueira Leite

• Advisor: Ricardo De Marco

Abstract

The micro-exon genes (MEGs) were recently identified in Schistosoma mansoni’s genome, worm responsible for schistosomiasis, a disease that affects more than 262 million people in more than 78 countries. Due to the capacity of variant protein production by alternative splicing of MEGs, preferential expression in certain life stages in contact with the definitive host, and the confirmation that many proteins coded by these genes are secreted to the external environment, It’s believed that these proteins have an important role in parasite-host relationship. The objective of this work was to study and characterize the structure and conformational dynamics of proteins coded by MEG-11 and MEG-14 and verify the interaction of Meg-14 protein with human proteins. The analysis of MEG-11 and MEG-14 proteins produced in recombinant system with circular dichroism (CD) shows that both proteins present secondary structures mostly disordered in aqueous solution. However, It was found that in presence of TFE, the dehydration of proteins and the increasing of temperature favor the surging of ordered structures. An increase of secondary structure was observed too for MEG-14 protein in presence of phospholipid vesicles and negative charged detergent micelles. These results support the identification of these proteins as classical intrinsically disordered proteins (IDPs) and opens the possibility of its interaction with different partners and factors related with the multifunctional roles and states in the host. Previous results of double-hybrid experiments pointed a possible interaction between MEG-14 and the human protein S100A9. By pulldown technique was possible confirm an calcium dependent interaction between these proteins. Additional analysis of MEG-14/S100A9 interaction with ITC and SPR experiments were able to calculate the dissociation constant between proteins equals to 2 μM. Finally, ex vivo experiments permit the ingestion of S100A9 coupled to a fluorescent molecule by S. mansoni, resulting in the accumulation of protein in the esophageal gland, where was localized the MEG-14 in S. japonicum, suggesting that the interaction observed in the in vitro experiments are occurring with the native MEG-14. (AU)

• FAPESP's process: 12/07288-7 - Study of structure, immunoreactivity and protein partners of proteins encoded by micro-exon genes of Schistosoma mansoni
• Grantee: Débora Orcia
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)