Endoplasmic reticulum as the site of lecithin formation in castor bean endosperm

Journal Article · Mon Jan 01 00:00:00 EST 1973 · J. Cell Biol.; (United States)

DOI:https://doi.org/10.1083/jcb.57.3.659· OSTI ID:6319110

Lord, J M; Kagawa, T; Moore, T S; Beevers, H

The properties of a discrete membranous fraction isolated on sucrose gradients from castor bean endosperm have been examined. This fraction was previously shown to be the exclusive site of phosphorylcholine-glyceride transferase. The distribution of NADPH-cytochrome c reductase and antimycin insensitive NADH-cytochrome c reductase across the gradient followed closely that of the phosphorylcholine-glyceride transferase. This fraction also had NADH diaphorase activity and contained cytochromes b/sub 5/ and P 450. On sucrose gradients containing 1 mM EDTA this fraction had a mean isopycnic density of 1.12 g/cm/sup 3/ and sedimented separately from the ribosomes; electron micrographs showed that it was comprised of smooth membranes. When magnesium was included in the gradients to prevent the dissociation of membrane-bound ribosomes, the isopycnic density of the membrane fraction with its associated enzymes was increased to 1.16 g/cm/sup 3/ and under these conditions the electron micrographs showed that the membranes had the typical appearance of rough endoplasmic reticulum. Together these data show that the endoplasmic reticulum is the exclusive site of lecithin formation in the castor bean endosperm and establish a central role for this cytoplasmic component in the biogenesis of cell membranes.

• Research Organization: Univ. of California, Santa Cruz, CA (United States)
• OSTI ID: 6319110
• Journal Information: J. Cell Biol.; (United States), Vol. 57:3
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CELL MEMBRANES
CELL CONSTITUENTS
LECITHINS
BIOSYNTHESIS
BIOCHEMICAL REACTION KINETICS
CARBON 14
CHOLINE
CYTOCHROMES
ENDOSPERM
ENZYME ACTIVITY
EXPERIMENTAL DATA
LABELLED COMPOUNDS
MAGNESIUM
PHASEOLUS
ALCOHOLS
ALKALINE EARTH METALS
AMINES
AMMONIUM COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON ISOTOPES
DATA
DRUGS
ELEMENTS
ESTERS
EVEN-EVEN NUCLEI
HYDROXY COMPOUNDS
INFORMATION
ISOTOPES
KINETICS
LEGUMINOSAE
LIGHT NUCLEI
LIPIDS
LIPOTROPIC FACTORS
MEMBRANES
METALS
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
PIGMENTS
PLANT TISSUES
PLANTS
QUATERNARY COMPOUNDS
RADIOISOTOPES
REACTION KINETICS
SYNTHESIS
YEARS LIVING RADIOISOTOPES
550201* - Biochemistry- Tracer Techniques