THE LARGE DIVERSE GENE FAMILY VAR ENCODES PROTEINS INVOLVED IN CYTOADHERENCE AND ANTIGENIC VARIATION OF PLASMODIUM-FALCIPARUM-INFECTED ERYTHROCYTES

The human malaria parasite Plasmodium falciparum evades host immunity by varying the antigenic and adhesive character of infected erythrocyt es. We describe a large and extremely diverse family of P. falciparum genes (var) that encode 200-350 kDa proteins having the expected prope rties of antigenically variant adhesion molecules. Predicted amino aci d sequences of var genes show a variable extracellular segment with do mains having receptor-binding features, a transmembrane sequence, and a terminal segment that is a probable submembrane anchor. There are 50 -150 var genes on multiple parasite chromosomes, and some are in clust ered arrangements. var probes detect two classes of transcripts in ste ady-state RNA: 7-9 kb var transcripts, and an unusual family of 1.8-2. 4 kb transcripts that may be involved in expression or rearrangements of var genes.