A group of Giardia lamblia variant-specific surface protein (VSP) genes with nearly identical 5′ regions

The surfaces of Giardia lamblia trophozoites contain one of a set of variant-specific surface proteins. The genes encoding these proteins are highly conserved at the 3′ terminus, but frequently demonstrate little similarity in the remainder of the coding region. This report describes a family of vsp genes highly similar to a repeat-containing vsp gene (vspC5) at the 5′ coding and flanking regions, but which diverge abruptly from vspC5 in the first repeat and do not themselves contain full copies of the repeat. This observation suggests the possibility that recombination among different vsp genes may have played a role in development of the vsp gene repertoire.