Golgi reassembly-stacking protein 2 ( GRS2) also known as Golgi reassembly-stacking protein of 55 kDa (GRASP55) is a protein that in humans is encoded by the GORASP2gene.[5] It was identified by its homology with GORASP1 and the protein's amino acid sequence was determined by analysis of a molecular clone of its complementary DNA.[6] The first (N-terminus) 212 amino acid residues of GORASP2 are highly homologous to those of GORASP1, but the remainder of the 454 amino acid residues are highly diverged from GORASP1.[6] The conserved region is known as the GRASP ___domain, and it is conserved among GRASPs of a wide variety of eukaryotes, but not plants.[5][7] The C-terminus portion of the molecule is called the SPR ___domain (serine, proline-rich).[7] GORASP2 is more closely related to homologues in other species, suggesting that GORASP2 is ancestral to GORASP1.[7] GORASP2 is found associated with the medial and trans cisternae of the Golgi apparatus.[7]
GORASP2 is involved in establishing the structure of the Golgi apparatus.[7][5] It is a peripheral membrane protein located on the Golgi cisterna, and it can bind to another GRS2 located on an adjacent cisterna through the GRASP ___domain, thus linking the cisternae together through multiple protein–protein interactions.[7][8]
GRS2 is attached to the membrane in two ways; it is myristylated, which attaches it directly to the lipid bilayer; it is also bound indirectly by binding to golgin-45, which binds to a Rab protein, which itself is lipidated and thus anchored to the membrane.[7]
The structure of the Golgi is disrupted during mitosis, and phosphorylation of the SPR domains of GORASP2 and GORASP1 regulate that disruption,[9][8]
GORASP2 may also be involved in forming Golgi ribbons, but the evidence is mixed.[7][9]
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