Molecular cloning and characterization o fplasmodium vivax hexose transporter

초록

Apicomplexan parasite include the causative agents of malaria and toxoplasmosis. They evolved from free-living form to intracellular parasite Plasmodium species. They are the most important cause of malaria, which kills above one million children each year. They lost many biosynthetic pathways and became reliant on their hosts as a nutrient source. They take up nutrients from their host cell through membranous transporters. To increase understanding of hexose transport in plasmodium vivax, we have carried out cloning and characterization of hexose transporter 1 (PvHT1). The PvHT1 gene from NCBI database was isolated using RT-PCR. The PvHT1 cDNA consisted of 1509 base pairs that encoded a 502 amino acids. Hydropathy analysis suggested 12 putative membrane-spanning domains. When expressed in Xenopus laevis oocytes, PvHT1 mediated the transport of [3H]deoxy-D-glucose (ddGlu) in an expression time- and incubation time-dependent manner without sodium dependency. The PvHT1 showed no exchange mode of glucose by efflux experiments. Concentration-dependency results showed saturable kinetics following Michaelis-Menten equation. The Eadie-Hofstee equation analysis revealed a Km value of 294.1 ?M and Vmax value of 1,060 pmol/oocyte/hr for [3H]ddGlu. The inhibition experiments showed strong inhibitory effect by glucose, mannose and ddGlu and mild effect by methyl?d-glucose. These results may give information for the molecular biological study of carbohydrate metabolism in Plasmodium vivax.