STUDIES OF MEMBRANE FORMATION IN TETRAHYMENA PYRIFORMIS

Abstract

When 1 1 4C-palmitic acid is used to pulse label logarithmic cultures of Tetrahymena pyriformis, radioactivity appears in lipids of the various membrane types at vastly differing rates . The microsomes and postmicrosomal supernatant attain a high specific radioactivity within 1 min, while the membranes enveloping the cilia require several hours to reach the microsomal level . A similar pattern is obtained when the tracer is sodium 11 4 0-acetate or 8,9 8H-hexadecyl glycerol . In all fractions the phosphonolipid incorporates radioactivity from 14C-palmitate much less rapidly than do the other major phospholipids . The patterns of labeling suggest that new lipids are transported from a cytoplasmic site of synthesis to points of membrane fabrication throughout the cell .

Membrane formation in Tetrahymena pyriformis. 4. Lipid composition and biochemical properties of Tetrahymena pyriformis membrane systems

“…However, as additional time elapsed following administration of the isotope, its relative distribution in cilia changed, so that the radioactivity was eventually apportioned in just the same pattern as is the mass of the lipids. One example of this changing lipid distribution pattern in cilia and other membrane fractions was presented earlier (Nozawa and Thompson, 1971b). Graphing the radioactivity in the three major phospholipids of palmitate-l4C-labeled cells revealed that in cilia (and, to a much lesser degree, in all other fractions) there was a gradual rise in the relative 4444 BIOCHEMISTRY, VOL.…”

“…Evidence pertinent to this question has been obtained by extending previous observations on the intracellular redistribution of radioactive lipids (Nozawa and Thompson, 1971b).…”

“…Cultures and Isolation of Lipids. Tetrahymena pyriformis, strain E, is cultured at 24°in an enriched proteose peptone medium with stirring as previously described (Thompson, Thompson (1971b).…”

“…Incubations with the radioactive tracers were carried out as described earlier (Nozawa and Thompson, 1971b), and the general labeling patterns were as reported in that publication.…”

Restricted lateral diffusion of surface membrane components in Tetrahymena thermophila

“…Antibodies to surface components of T. thermophila were prepared by immunising rabbits subscapularly with an emulsion of pellicles (prepared according to [6]) in complete Freunds adjuvant. Boosting injections were administered in weeks 3 and 7.…”