The Golgi apparatus, also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles inside the cell before the vesicles are sent to their destination. It resides at the intersection of the secretory, lysosomal, and endocytic pathways. It is of particular importance in processing proteins for secretion, containing a set of glycosylation enzymes that attach various sugar monomers to proteins as the proteins move through the apparatus.
COPI is a coatomer, a protein complex that coats vesicles transporting proteins from the cis end of the Golgi complex back to the rough endoplasmic reticulum (ER), where they were originally synthesized, and between Golgi compartments. This type of transport{{Clarify|reason=does this include the transport between the Gologi compartments) is retrograde transport, in contrast to the anterograde transport associated with the COPII protein. The name "COPI" refers to the specific coat protein complex that initiates the budding process on the cis-Golgi membrane. The coat consists of large protein subcomplexes that are made of seven different protein subunits, namely α, β, β', γ, δ, ε and ζ.
ADP-ribosylation factor 6 (ARF6) is a member of the ADP ribosylation factor family of GTP-binding proteins. ARF6 has a variety of cellular functions that are frequently involved in trafficking of biological membranes and transmembrane protein cargo. ARF6 has specifically been implicated in endocytosis of plasma membrane proteins and also, to a lesser extent, plasma membrane protein recycling.
The coatomer is a protein complex that coats membrane-bound transport vesicles. Two types of coatomers are known:
ADP-ribosylation factor 1 is a protein that in humans is encoded by the ARF1 gene.
ADP-ribosylation factor-binding protein GGA3 is a protein that in humans is encoded by the GGA3 gene.
General vesicular transport factor p115 is a protein that in humans is encoded by the USO1 gene.
Cytohesin-2 is a protein that in humans is encoded by the CYTH2 gene.
Cytohesin-1 formerly known as Pleckstrin homology, Sec7 and coiled/coil domains 1 (PSCD1) is a protein that in humans is encoded by the CYTH1 gene.
ADP-ribosylation factor 3 is a protein that in humans is encoded by the ARF3 gene.
ADP-ribosylation factor GTPase-activating protein 1 is an enzyme that in humans is encoded by the ARFGAP1 gene. Two transcript variants encoding different isoforms have been found for this gene.
Coatomer subunit epsilon is a protein that in humans is encoded by the COPE gene.
Golgin subfamily A member 4 is a protein that in humans is encoded by the GOLGA4 gene.
ADP-ribosylation factor 5 is a protein that in humans is encoded by the ARF5 gene.
ADP-ribosylation factor 4 is a protein that in humans is encoded by the ARF4 gene.
Arf-GAP with SH3 domain, ANK repeat and PH domain-containing protein 2 is a protein that in humans is encoded by the ASAP2 gene.
GTP-binding protein ARD-1 is a protein that in humans is encoded by the TRIM23 gene.
Arfaptin-2 is a protein that in humans is encoded by the ARFIP2 gene.
Arf-GAP with Rho-GAP domain, ANK repeat and PH domain-containing protein 1 is a protein that in humans is encoded by the ARAP1 gene.
The Golgi matrix is a collection of proteins involved in the structure and function of the Golgi apparatus. The matrix was first isolated in 1994 as an amorphous collection of 12 proteins that remained associated together in the presence of detergent and 150 mM NaCl. Treatment with a protease enzyme removed the matrix, which confirmed the importance of proteins for the matrix structure. Modern freeze etch electron microscopy (EM) clearly shows a mesh connecting Golgi cisternae and associated vesicles. Further support for the existence of a matrix comes from EM images showing that ribosomes are excluded from regions between and near Golgi cisternae.
