ISOLATION AND BIOCHEMICAL-CHARACTERIZATION OF THE PLASMA-MEMBRANE OF TRITRICHOMONAS-FETUS

A fraction containing plasma membrane-enriched vesicles has been prepa red from Tritrichomonas foetus. Cells were ruptured using a Potter typ e homogenizer, under well controlled conditions, and membranes were is olated by differential centrifugation and in discontinuous sucrose gra dient. This fraction was enriched 8 and 10-fold in the plasma membrane marker enzymes 5'-nucleotidase and (Na++K+)-dependent, ouabain-sensit ive ATPase, respectively. Determination of Glucose-6-phosphatase and N ADPH cytochrome c reductase activities in this fraction, indicates a m inimal contamination with endoplasmic reticulum membranes. Analysis by Sodium Dodecyl Sulfate-Polyacrylamide (SDS-PAGE) gradient gel showed that the plasma membrane fraction contains several proteins with major bands corresponding to apparent molecular weights of 48, 45, 39, 37, 32, 30, 27, 23, 20, 19, 17, and 15 kDa.