The Journal of Cell Biology, Vol 67, 700-714, Copyright © 1975 by The Rockefeller University Press
Biogenesis of microsomal membrane glycoproteins in rat liver. II. Purification of soluble glycoproteins and their incorporation into microsomal membranes
F Autuori, H Svensson and G Dallner
Sialoproteins isolated from the soluble fraction of rat liver could be
incorporated into microsomal membranes. This incorporation was dependent on
protein concentration, time, and temperature. Sodium dodecyl sulfate gel
electrophoresis of membrane proteins after in vitro incorporation showed
four major sugar-containing peaks and was similar to that found after in
vivo labeling. Most of the incorporated protein was tightly bound to the
microsomal membrane. Gel filtration and ion- exchange chromatography
revealed the presence of several cytosolic glycoproteins that could be
incorporated into microsomes. During prolonged centrifugation in a KBr
solution with a density of 1.21 a highly labeled ([3H]glucosamine) protein
(mole wt approximately to 70,000) that was actively incorporated into
microsomes could be recovered in the upper region of the tube. These
results demonstrate that several cytoplasmic glycoproteins of rat liver are
transferred into microsomal membranes and that one of these is a
lipoprotein.
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