Characterisation and translation studies of messenger RNA from the human malaria parasite Plasmodium falciparum and construction of a cDNA library.

RNA was isolated from trophozoites, schizonts and mixed populations of Plasmodium falciparum. 5% of the total was poly(A+) message, of average length 1.2 kb (10-12 kb maximum) and a poly(A) content of 10%. The mRNA fractions could be translated in vitro by reticulocyte lysates supplemented either with exogenous or P. falciparum tRNA. The patterns from two independent isolates, one cloned (T9-94) and one uncloned (K1) were virtually identical. Major translation products from 16-230 kDa have been measured. The most abundant is lactate dehydrogenase (34.8 kDa). Trophozoite mRNA codes principally for proteins of less than or equal to 93 kDa, while schizont mRNA codes for additional proteins of higher molecular mass. There are marked similarities between the in vitro translation products and proteins synthesised in vivo in synchronous cultures. A number of schizont mRNA translation products (principally those of 230, 203, 185, 170, 115, 101 and 71 kDa) are specifically precipitated without post-translational modification by sera from humans exposed to malaria. A cDNA library has been constructed in phage lambda from total poly(A+) RNA and partially characterised. About 10% of the clones derive from abundant mRNA sequences. Putative actin clones have been isolated from this library and the parasite actin mRNA sized at approx. 2.8 kb.