[Isoelectric focusing of plasma membrane proteins from Strongylocentrotus intermedius sea urchin embryo cells].

14C-amino acids were introduced into the developing sea urchin embryos S. intermedius in 7,5 hours after the fertilization (middle blastula stage). In 30 min the embryos development were terminated, the plasma membrane was isolated and 14C-labelled proteins were recovered from the membrane with 8 M urea and separated by isoelectrofocusing in pH gradient 3,5-10 in presence of 6 M urea. All 14C-label was introduced into two proteins with pI 4,85-4,90 and 5,20-5,25 and the proteins were effectively separated. The minimal molecular weight of the proteins estimated by SDS-acrylamide gel-electrophoresis was 10 000 and 15 000 daltons, respectively.