Plasmodium falciparum: comparison of the genomic organization of the knob protein gene in knobby and knobless variants.

The genomic organization of the knob protein (KP) gene of knobby (K+) and knobless (K-) variants of the Thai isolate NT 108 and the Gambian isolate FCR-3 are compared. The restriction enzyme maps and the chromosomal location of the KP gene of K+ variants of both isolates are apparently identical. A comparison of the susceptibility of the KP gene to deletions and the extent of deletion of chromosomal DNA in K- variants of each geographical isolate suggests isolate-specificity of the stability of the deleted DNA sequences. With the exception of a mutant K- population of FCR-3, which could not be distinguished from K+ FCR-3, in all other K- variants of both geographical isolates the deletion of the KP gene was accompanied by the loss of several hundred base pairs of DNA from chromosome 2. The deletion resulted in the localization of the mutant KP gene in proximity to telomeric DNA sequences.