IDENTIFICATION OF MAJOR PROTEINS ASSOCIATED WITH DICTYOSTELIUM-DISCOIDEUM ENDOCYTIC VESICLES

Magnetic isolation of endocytic vesicles from Dictyostelium discoideum was accomplished after feeding the amoebae with iron oxide particles. Proteins associated with the endocytic vesicles were resolved by SDS- PAGE and digested 'in-gel' with endoproteinase Lys-C or Asp-N to gener ate peptides for amino acid sequencing, This strategy allowed the iden tification of the major protein constituents of the vesicles: namely, the A, B, D, E and 110 kDa subunits of a vacuolar type H+-ATPase, acti n, a Rab 7-like GTPase, a p34 protein corresponding to a new cysteine proteinase and the 25 kDa product of a recently sequenced D. discoideu m open reading frame.