The gene product of the Plasmodium falciparum 11.1 locus is a protein larger than one megadalton.

The Plasmodium falciparum 11.1 gene locus on chromosome 10 extends over 30 kb and contains approximately 22 kb of a tandemly repeated 27-bp sequence. Biochemical and size similarities have been noted between the reported 11.1 antigen and a variable-Mr, surface-radioiodinatable protein which appears to be involved in the cytoadherence of red blood cells infected with mature intraerythrocytic parasites to venular endothelium. We attempted to determine if these proteins were identical. Using rabbit antibody and affinity purified human immune sera specific for peptides encoded by the 27-bp repeat and a flanking 5' region, we have shown that the 11.1 locus encodes a protein of more than 1000 kDa. This protein cross-reacts with an uncharacterized 260-kDa protein, previously identified as the gene product of the 11.1 locus, and Pf155-RESA, but not with the radioiodinatable protein. The 11.1 protein that we have identified is a malarial protein of unprecedented size.