Involved in transport of proteins from the cis/medial-Golgi to the trans-Golgi network. Part of a unique SNARE complex composed of the Golgi SNAREs GOSR1, STX5 and YKT6 (By similarity). Interacts (via IxM motif) with SEC24C and SEC24D; mediates GOSR2 packaging into COPII-coated vesicles (PubMed:18843296). Concentrated most in the intermediate compartment/cis-Golgi network and the cis-Golgi cisternae 1 and 2. Greatly reduced in concentration at the trans end of the Golgi apparatus. The disease is caused by variants affecting the gene represented in this entry. Belongs to the GOSR2 family.