Intramembranous particles are clustered on microvillus membrane vesicles.
Many intramembranous particles in pig jejunal microvillus membranes cluster during cell disruption and membrane vesiculation with the MgCl2 aggregation technique (Hauser, H., Howell, K., Dawson, R.M.C. and Bowyer, D.E. (1980) Biochim. Biophys. Acta 602, 567-577). Isolated brush borders and purified microvillus membrane vesicles were jet-frozen and examined by freeze-fracture electron microscopy. From 30 to 60% of purified vesicles exhibited no intramembranous particles on their fracture face and 22-39% exhibited clustered or aggregated intramembranous particles. Only 6-15% of the vesicles exhibited the random distribution of intramembranous particles that is characteristic of intact enterocytes. Aggregation was not reversed after dialysis to remove divalent cations. Prior freezing of tissue or vesicles (-70 degrees C) gave the same results as fresh unfrozen material. Heterogeneity of microvillus vesicles may occur among the vesicles generated from a single microvillus.
D000818:Animals; D005614:Freeze Fracturing; D007583:Jejunum / Q000378:metabolism / Q000648:ultrastructure; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D008563:Membrane Lipids / Q000302:isolation & purification*; D008565:Membrane Proteins / Q000302:isolation & purification*; D008854:Microscopy, Electron; D008871:Microvilli / Q000378:metabolism* / Q000648:ultrastructure; D010316:Particle Size; D013552:Swine
D008563:Membrane Lipids; D008565:Membrane Proteins; D015636:Magnesium Chloride; D008274:Magnesium