Expression of the major surface antigen of Plasmodium knowlesi sporozoites in yeast

The circumsporozite protein, a surface antigen of the sporozoite stage of the monkey malarial parasite Plasmodium knowlesi, was expressed in the yeast Saccharomyces cerevisiae by using an expression vector containing the 5' regulatory region of the yeast alcohol dehydrogenase I gene. It was necessary to eliminate the entire 5' upstream region of the parasite DNA to obtain the expression of this protein. Only the circumsporozoite precursor was produced by the yeast transformants, as detected by immunoblotting. About 55 and 20 percent of the circumsporozoite protein produced in yeast was associated wtih the 25,000 g and 150,000 g particulate fractions, respectively. The protein could be solubilized in Triton X-100 and was stable in solubilized extracts.