Objective:To analyse the rar gene repertoire and characterise the rhondroitin sulphate A (CSA)-binding activity of the Duffy-binding like(I)BI.) domains encoded by the var2csa gene of a Plasmodium falciparum(P.falciparum) isolate in Hainan Province,China.Methods:The sequences of var DBL1 regions were PCR-amplified,sequenced and the sequence characteristics was bioinformalically analysed.Recombinant proteins encoded by the var2csa genes were expressed and purified.The binding activities of the recombinant proteins to CSA receptor was detected by ELISA assays.Results:Fifty six unique DBI.a sequences were obtained,and the sequences represented similar diversity to the var genes of the genome parasite 3D7.There are two var2csa genes in the P.falciparum isolated from Hainan Province.Unlike in other falciparum parasites such as HB3,the two var2csa genes are more diverged.The receptor-binding capacity of DBL-5εand DBI.-6 e domains of HN var2CSA was studied.Conclusions:This work represented the diversity of rar genes of a P.falciparum isolate in China.
Ning JiangLi MengHui-Jun LuWei KangShuai PengWei-Qing PanJi-Gang YinQi-Jun Chen
Background During the blood stage of malaria infection, parasites internalize in the host red blood cells and degrade massive amounts of hemoglobin for their development. Although the morphology of the parasite＇s hemoglobin uptake pathway has been clearly observed, little has been known about its molecular mechanisms. Methods The recombinant proteins from Plasmodium falciparum, dynamin like protein 1 （PfDYN1） and 2 （PfDYN2） GTPase domain, were expressed in E .coil and showed GTPase activity. By using a dynamin inhibitor, dynasore, we demonstrated the involvement of PfDYN1 in the hemoglobin uptake pathway. Results The GTPase activity of the two recombinant proteins was inhibited by dynasore in vitro. Treatment of parasite cultures with 80 μmol/L dynasore at the ring and early trophozoite stage resulted in substantial inhibition of parasite growth and in an obvious decline of hemoglobin quantum. Furthermore, reduced intracellular hemozoin accumulation and decreased uptake of the FITC-dextran were also observed, together with distinctive changes in the ultrastructure of parasites after the dynasore treatment. Conclusions Our results show that PfDYN1 plays an important role in the hemoglobin uptake pathway of P. falciparum and suggest its possibility of being a novel target for malaria chemotherapy.
