The large diverse gene family var encodes proteins involved in cytoadherence and antigenic variation of plasmodium falciparum-infected erythrocytes

Abstract

The human malaria parasite Plasmodium falciparum evades host immunity by varying the antigenic and adhesive character of infected erythrocytes. We describe a large and extremely diverse family of P. falciparum genes ( var) that encode 200–350 kDa proteins having the expected properties of antigenically variant adhesion molecules. Predicted amino acid sequences of var genes show a variable extracellular segment with domains 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 clustered arrangements. var probes detect two classes of transcripts in steady-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 re-arrangements of var genes.