Although P. vivax has fewer multigene families than some other Plasmodium species, the vir family is large and contains between 600 and 1000 gene copies arrayed throughout the subtelomeric regions. The family can be divided into six subfamilies. Each gene has three exons: 1) a short exon lacking a signal sequence, 2) a longer exon with predicted transmembrane region and four conserved cysteines, and 3) an exon with a highly conserved region. The VIR protein encodes an immunovariant protein that may function in immune evasion. It consists of three major conserved blocks separated by variable regions.