Exocyst

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An exocyst is a protein complex with an octameric quaternary structure.

The protein subunits that comprise the exocyst aggregate in a polar fashion. In mammalian cells and in Saccharomyces cerevisiae, there are eight subunits: Sec3p, Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, Exo70p, and Exo84p.

As a whole, the exocyst complex functions to fuse protein carrying vesicles to the plasma membrane, in order to enable exocytosis. The proteins on one end of the exocyst complex recognize Rab GTPases on secretory vesicles, while those on the other end localize to the plasma membrane, most likely through interactions with Rho GTPases responsible for controlling cell polarity and the activity of the cytoskeleton. The proteins in between may act as a structural core to transmit information between the two membranes.

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http://www.jbc.org/cgi/content/full/279/41/43027