Insights into structural and regulatory roles of Sec16 in COPII vesicle formation at ER exit sites.

COPII-coated buds are formed at endoplasmic reticulum exit sites (ERES) to mediate ER-to-Golgi transport. Sec16 is an essential factor in ERES formation, as well as in COPII-mediated traffic in vivo. Sec16 interacts with multiple COPII proteins, although the functional significance of these interactions remains unknown. Here we present evidence that ...
full-length Sec16 plays an important role in regulating Sar1 GTPase activity at the late steps of COPII vesicle formation. We show that Sec16 interacts with Sec23 and Sar1 through its C-terminal conserved region and hinders the ability of Sec31 to stimulate Sec23 GAP activity toward Sar1. We also find that purified Sec16 alone can self-assemble into homo-oligomeric complexes on a planar lipid membrane. These features ensure prolonged COPII coat association within a preformed Sec16 cluster, which may lead to the formation of ERES. Our results indicate a mechanistic relationship between COPII coat assembly and ERES formation.
Mesh Terms:
Biological Transport, COP-Coated Vesicles, Endoplasmic Reticulum, GTPase-Activating Proteins, Membrane Proteins, Membranes, Monomeric GTP-Binding Proteins, Protein Binding, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Vesicular Transport Proteins
Mol. Biol. Cell
Date: Aug. 01, 2012
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