title: Sterol-deficient domains correlate with intramembrane particle arrays in the plasma membrane of Chlamydomonas reinhardii.
abstract: The planar distribution of 3-beta-hydroxysterols in the plasmalemma of the green flagellate Chlamydomonas reinhardii has been studied with the freeze-fracture technique using the polyene antibiotic filipin and the saponin tomatin as cytochemical markers. Filipin-sterol complexes were predominantly observed as 25 to 30 nm protuberances on the E-face of the plasmalemma with corresponding invaginations on the P-face. Generally filipin-sterol and tomatin-sterol complexes were randomly distributed, but were virtually absent from sites of intramembrane particle arrays (IMP-arrays, i.e. the flagellar necklace, the flagellar bracelet including strut arrays, the eyespot membrane). The results suggest that IMP-arrays of Chlamydomonas are deficient in 3-beta-hydroxysterols and may therefore be regarded as special lipid arrays. IMP-arrays might require an altered lipid environment for proper function. Some functional aspects of IMP-arrays in Chlamydomonas are discussed.
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure*; D002696:Chlamydomonas / Q000648:ultrastructure*; D005372:Filipin / Q000378:metabolism; D005614:Freeze Fracturing; D008854:Microscopy, Electron; D013261:Sterols; D014053:Tomatine / Q000378:metabolism
chemical_list: D013261:Sterols; D014053:Tomatine; D005372:Filipin