title: Isolation and characterization of the Neurospora crassa endoplasmic reticulum.
abstract: The endoplasmic reticulum from Neurospora crassa was identified by monitoring the activity of the putative enzyme marker phosphatidylcholine glyceride transferase. After differential centrifugation of a cell homogenate, phosphatidylcholine glyceride transferase activity initially copurified with plasma membrane H+-ATPase. However, isopycnic centrifugation of the whole-cell homogenate on a linear sucrose gradient separated the two enzyme activities into different fractions. The lighter membrane fraction exhibited characteristics that have been associated with the endoplasmic reticulum in other organisms: (i) the inclusion of magnesium caused this light membrane fraction to shift to a higher density on the gradient; (ii) it was highly enriched in cytochrome c reductase, an endoplasmic reticulum marker in other systems; and (iii) the morphology of the light fraction with and without added magnesium was clearly distinguishable from that of the plasma membrane fraction by electron microscopy. A reinvestigation of the location of chitin synthetase confirmed its association with the plasma membrane fraction even after separation of the lighter fractions.
mesh_terms: D000251:Adenosine Triphosphatases / Q000302:isolation & purification; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D002687:Chitin Synthase / Q000378:metabolism; D002798:Diacylglycerol Cholinephosphotransferase / Q000302:isolation & purification / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000648:ultrastructure; D005952:Glucose-6-Phosphatase / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008854:Microscopy, Electron; D009245:NADH Dehydrogenase / Q000378:metabolism; D009491:Neurospora / Q000648:ultrastructure*; D009492:Neurospora crassa / Q000201:enzymology / Q000648:ultrastructure*; D010770:Phosphotransferases / Q000378:metabolism*
chemical_list: D009245:NADH Dehydrogenase; D002687:Chitin Synthase; D010770:Phosphotransferases; D002798:Diacylglycerol Cholinephosphotransferase; D005952:Glucose-6-Phosphatase; D000251:Adenosine Triphosphatases; D008274:Magnesium