INVITRO TRANSLATION OF PLASMODIUM-FALCIPARUM ALDOLASE IS NOT INITIATED AT AN UNUSUAL SITE

It has been proposed recently that translation of fructose-1,6-diphosphate aldolase of the malaria parasite Plasmodium falciparum is initiated at a UAG codon, both in the parasite and in a rabbit reticulocyte cell-free translation system. We have introduced mutations around that UAG codon and find that cell-free expression of a construct encoding an AUG in this position results in a slightly larger translation product. The translation product of the construct encoding the UAG codon is of the same apparent molecular weight as the products obtained from two other constructs; one in which the UAG is replaced by AAG, and one in which nucleotides upstream from a second AUG codon are deleted. Thus we show that translation is not initiated at the UAG and conclude that synthesis of aldolase in the parasite starts at an AUG, provided after splicing of pre-mRNA.