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Mol. Cell. Biol., Jan 1997, 256-266, Vol 17, No. 1
BL Tang, F Peter, J Krijnse-Locker, SH Low, G Griffiths and W Hong
The role of COPII components in endoplasmic reticulum (ER)-Golgi transport,
first identified in the yeast Saccharomyces cerevisiae, has yet to be fully
characterized in higher eukaryotes. A human cDNA whose predicted amino acid
sequence showed 70% similarity to the yeast Sec13p has previously been
cloned. Antibodies raised against the human SEC13 protein (mSEC13)
recognized a cellular protein of 35 kDa in both the soluble and membrane
fractions. Like the yeast Sec13p, mSEC13 exist in the cytosol in both
monomeric and higher-molecular-weight forms. Immunofluorescence microscopy
localized mSEC13 to the characteristic spotty ER-Golgi intermediate
compartment (ERGIC) in cells of all species examined, where it colocalized
well with the KDEL receptor, an ERGIC marker, at 15 degrees C.
Immunoelectron microscopy also localized mSEC13 to membrane structures
close to the Golgi apparatus. mSEC13 is essential for ER-to-Golgi
transport, since both the His6-tagged mSEC13 recombinant protein and the
affinity-purified mSEC13 antibody inhibited the transport of restrictive
temperature-arrested vesicular stomatitis virus G protein from the ER to
the Golgi apparatus in a semi-intact cell assay. Moreover, cytosol
immunodepleted of mSEC13 could no longer support ER-Golgi transport.
Transport could be restored in a dose- dependent manner by a cytosol
fraction enriched in the high-molecular- weight mSEC13 complex but not by a
fraction enriched in either monomeric mSEC13 or recombinant mSEC13. As a
putative component of the mammalian COPII complex, mSEC13 showed partially
overlapping but mostly different properties in terms of localization,
membrane recruitment, and dynamics compared to that of beta-COP, a
component of the COPI complex.
Copyright © 1997, American Society for Microbiology
The mammalian homolog of yeast Sec13p is enriched in the intermediate compartment and is essential for protein transport from the endoplasmic reticulum to the Golgi apparatus
Membrane Biology Laboratory, National University of Singapore, Republic of Singapore.
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