Selectivity of yolk protein uptake: Comparison of vitellogenins of two insects

The vitellogenins of Hyalophora cecropia and Blattella germanica have similar Stokes' radii (69 and 75Å), sedimentation coefficients (15.9 and 16.8S) and isoelectric points (pH 5.7 and 5.0), and share similar amino acid compositions with vitellogenins of other animals. The two vitellogenins show no immunological crossreaction. Blattella oöcytes take up their own vitellogenin in vivo at a rapid rate and that of Hyalophora at a low rate comparable to that of a non-vitellogenic protein. Hyalophora oöcytes take up their own vitellogenin rapidly in vitro and Blattella vitellogenin only at a negligible rate. Molecular weights, shapes and charges of the vitellogenins are similar to non-vitellogenins and form no basis for selective uptake.