The exocyst is an octameric protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 complex involved in vesicle

Vesicle (biology)

A vesicle is a bubble of liquid within another liquid, a supramolecular assembly made up of many different molecules. More technically, a vesicle is a small membrane-enclosed sack that can store or transport substances. Vesicles can form naturally because of the properties of lipid membranes , or...

 trafficking, specifically the tethering and spatial targeting of post-Golgi vesicles to the plasma membrane prior to vesicle fusion. It is implicated in a number of cell processes, including exocytosis

Exocytosis

Exocytosis , also known as 'The peni-cytosis', is the durable process by which a cell directs the contents of secretory vesicles out of the cell membrane...

 and also cell migration and growth.

Subunits

The exocyst is composed of eight subunits that aggregate in a polar fashion. In mammalian cells and in Saccharomyces cerevisiae, there are eight subunits: EXOC1

EXOC1

Exocyst complex component 1 is a protein that in humans is encoded by the EXOC1 gene.-Further reading:...

, EXOC2

EXOC2

Exocyst complex component 2 is a protein that in humans is encoded by the EXOC2 gene.-Further reading:...

, EXOC3

EXOC3

Exocyst complex component 3 is a protein that in humans is encoded by the EXOC3 gene.-Interactions:EXOC3 has been shown to interact with DLG3 and EXOC4.-Further reading:...

, EXOC4

EXOC4

Exocyst complex component 4 is a protein that in humans is encoded by the EXOC4 gene.-Interactions:EXOC4 has been shown to interact with DLG4, EXOC7, GRIN2B, EXOC3 and DLG3.-Further reading:...

, EXOC5

EXOC5

Exocyst complex component 5 is a protein that in humans is encoded by the EXOC5 gene.-Further reading:...

, EXOC6, EXOC7

EXOC7

-Interactions:EXOC7 has been shown to interact with EXOC4 and RHOQ.-Further reading:...

, and EXOC8

EXOC8

Exocyst complex component 8 is a protein that in humans is encoded by the EXOC8 gene.-Further reading:...

. These subunits were formerly known as Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84, although they have been recently renamed.

Function

The exocyst complex serves to direct vesicles after the Golgi complex to specific locations on the plasma membrane and to mediate their tethering and localization to the membrane immediately before fusion. Because of this function, the exocyst complex is heavily involved in exocytosis

Exocytosis

Exocytosis , also known as 'The peni-cytosis', is the durable process by which a cell directs the contents of secretory vesicles out of the cell membrane...

. Sec3 (EXOC1) and Exo70 (EXOC7) are localized to the plasma membrane, and are physically attached to the membrane by Rho GTPases

Rho family of GTPases

The Rho family of GTPases is a family of small signaling G protein , and is a subfamily of the Ras superfamily. The members of the Rho GTPase family have been shown to regulate many aspects of intracellular actin dynamics, and are found in all eukaryotic organisms including yeasts and some plants...

 such as CDC42

CDC42

Cell division control protein 42 homolog also known as CDC42 is a protein involved in regulation of the cell cycle. In humans, CDC42 is encoded by the CDC42 gene.- Function :...

. Other complementary exocyst components such as Sec15 (EXOC6) and Sec4 are localized to the vesicle membrane. Exocyst proteins on the plasma membrane bind vesicular exocyst proteins, bringing the vesicle very close to the plasma membrane in a fashion similar to the SNARE

SNARE (protein)

SNARE proteins are a large protein superfamily consisting of more than 60 members in yeast and mammalian cells....

 interactions to facilitate fusion.

The exocyst also interacts with Rho GTPases responsible for controlling cell polarity and the activity of the cytoskeleton

Cytoskeleton

The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within a cell's cytoplasm and is made out of protein. The cytoskeleton is present in all cells; it was once thought to be unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton...

.

External links

• http://www.umassmed.edu/faculty/graphics/208/munson-figure-1.jpg
• http://www.jbc.org/cgi/content/full/279/41/43027