Background: Plasmodium, the causative agent of malaria, exports many proteins to the surface of the infected red blood cell (iRBC) in order to modify it toward a structure more suitable for parasite development and survival. One such exported protein, SURFIN_4.2, from the parasite of human malignant malaria, P. falciparum, was identified in the trypsin-cleaved protein fraction from the iRBC surface, and is thereby inferred to be exposed on the iRBC surface. SURFIN_4.2 also localize to Maurer’s clefts—parasite-derived membranous structures established in the RBC cytoplasm and tethered to the RBC membrane—and their role in trafficking suggests that they are a pathway for SURFIN_4.2 transport to the iRBC surface. It has not been determined the participation of protein domains and motifs within SURFIN_4.2 in transport from Maurer’s clefts to the iRBC surface; and herein we examined if the SURFIN_4.2 intracellular region containing tryptophan-rich (WR) domain is required for its exposure on the iRBC surface. Results: We generated two transgenic parasite lines which express modified SURFIN_4.2, with or without a part of the intracellular region. Both recombinant SURFIN_4.2 proteins were exported to Maurer’s clefts. However, only SURFIN_4.2 possessing the intracellular region was efficiently cleaved by surface treatment of iRBC with proteinase K. Conclusions: These results indicate that SURFIN_4.2 is exposed on the iRBC surface and that the intracellular region containing WR domain plays a role on the transport from Maurer’s clefts to the iRBC membrane.

Dynamic knee valgus is considered a risk factor of non-contact anterior cruciate ligament (ACL) injury. To identify athletes at a higher risk, we developed a two-dimensional (2D) video-based screening test that determines hip abductor function as well as dynamic hindfoot and knee valgus. The purpose of this study was to validate the accuracy of the indices for dynamic knee valgus derived knee-in distance (KID) and hip-out distance (HOD) from the 2D-video.Twenty healthy university students agreed to participate in this study. Subjects were asked to step off a 30-cm box and land on one leg. This procedure was recorded simultaneously using a 2D video camera in the frontal plane and the Vicon motion capture system. Pearson's correlations examined associations between KID, KID normalized by height (KID/H), HOD, as well as HOD normalized by height (HOD/H) and 3D-valgus (knee valgus) or 3D-IR (tibial internal rotation).Significant correlations were found between the KID and 3D-valgus (r=0.72, p<0.01) and KID/H and 3D-valgus (r=0.73, p<0.01). Associations were not significant between KID and 3D-IR (r=0.08) and between KID/H and 3D-IR (r=0.03). A positive moderate correlation between HOD and 3D-valgus (r=0.46, p<0.05) and HOD/H and 3D-valgus (r=0.50, p<0.05), as well as a negative moderate correlations between HOD and 3D-IR (r=-0.52, p<0.05) and between HOD/H and 3D-IR (r=-0.51, p<0.05) were also observed.We conclude that KID is a reliable alternative for the 3D-valgus and the HOD is for the 3D-valgus and tibial external rotation.

Background: Plasmodium, the causative agent of malaria, exports many proteinsto the surface of the infected red blood cell (iRBC) in order to modify ittoward a structure more suitable for parasite development and survival. Onesuch exported protein, SURFIN_4.2, from the parasite of humanmalignant malaria, P. falciparum, wasidentified in the trypsin-cleaved protein fraction from the iRBC surface, andis thereby inferred to be exposed on the iRBC surface. SURFIN_4.2 alsolocalize to Maurer’s clefts – parasite-derived membranous structures establishedin the RBC cytoplasm and tethered to the RBC membrane – and their role intrafficking suggests that they are a pathway for SURFIN_4.2 transportto the iRBC surface. It has not been determined the participation of proteindomains and motifs within SURFIN_4.2 in transport from Maurer’sclefts to the iRBC surface; and herein we examined if the SURFIN_4.2 intracellularregion containing tryptophan-rich (WR) domain is required for its exposure on theiRBC surface. Results: We generated two transgenic parasite lineswhich express modified SURFIN_4.2, with or without a part of the intracellularregion. Both recombinant SURFIN_4.2 proteins were exported to Maurer’sclefts. However, only SURFIN_4.2 possessing the intracellular region wasefficiently cleaved by surface treatment of iRBC with proteinase K. Conclusions: These results indicate that SURFIN_4.2is exposed on the iRBC surface and that the intracellular region containing WRdomain plays arole on the transport from Maurer’s clefts to the iRBC membrane.