Vaults are highly conserved among vertebrate species and have been purified to apparent homogeneity from rat, rabbit, mouse, chicken, cow, bullfrog (Rana Catesbeiana), the South African clawed frog Xenopus Laevis, sea urchin, Dictyostelium, and Acanthamoeba (Kedersha et al., 1990).
Below: Purified vaults from rat (left), bullfrog (center) and rabbit (right).
They have been purified to near homogeneity from human cells (HeLa and the MDR line GLC4/ADR). Vaults from diverse species are nearly identical in size, shape and morphology (see figure above). Minor variations have been noted in the size of the major vault protein, but antibodies raised against rat vaults recognize the major vault protein in nearly all eukaryotic species tested including man, dog and Drosophila. Vaults from Dictyostelium appear more heterogenous than those from the vertebrates due to the presence of two forms, an "intact" vault which is nearly identical to those seen in the vertebrates and a "half" vault which appears to be formed by cleavage or separation perpendicular to the longitudinal axis Vasu et al., 1993, Vasu and Rome, 1995. On Western blots, the Dictyostelium vaults cross react with the anti-rat vault antiserum. The level of expression of the major vault protein in Dictyostelium is quite high, although the major vault protein is seen as a doublet rather than a single bandand is actually three related albeit separate proteins ( see below). The level of expression of the Dictyostelium MVPs are relatively constant during aggregation and fruiting, suggesting a need for these particles throughout Dictyostelium development (Vasu et al., 1993, Vasu and Rome, 1995).