Surfeit locus protein 4 is a protein that in humans is encoded by the SURF4 gene. This gene is located in the surfeit gene cluster, which is comprised of very tightly linked housekeeping genes that do not share sequence similarity. The encoded protein is a conserved integral membrane protein containing multiple putative transmembrane regions. In eukaryotic cells, protein transport between the endoplasmic reticulum and Golgi compartments is mediated in part by non-clathrin-coated vesicular coat proteins (COPs). The specific function of this protein has not been determined but its yeast homolog is directly required for packaging glycosylated pro-alpha-factor into COPII vesicles. This gene uses multiple polyadenylation sites, resulting in transcript length variation. The existence of alternatively spliced transcript variants has been suggested, but their validity has not been determined. [provided by RefSeq].
May play a role in the maintenance of the architecture of the endoplasmic reticulum-Golgi intermediate compartment and of the Golgi.