Plays a role in transport between endoplasmic reticulum and Golgi. In pancreatic beta cells, required to transport proinsulin from endoplasmic reticulum into the Golgi (PubMed:33164986). Interacts with the COPII coat components Sec23 (SEC23A and/or SEC23B) and Sec24 (SEC24A and/or SEC24B) (PubMed:11489904). Interacts with YIF1A (PubMed:15990086). May interact with RAB1A (PubMed:15611160). Interacts with YIPF3 and YIPF4 (PubMed:27999994). Enriched at the endoplasmic reticulum exit sites (By similarity). Incorporated into COPII-coated vesicles (By similarity). Ubiquitously expressed with abundant expression in pancreatic tissue, islets, beta cells, and brain. Highly expressed in coronary smooth muscles. Expressed in developing cortex at all stages examined but most strikingly at 12 gestational weeks. Expression is found in both progenitor (ventricular zone) and neuronal (intermediate zone and cortical plate) compartments. Also selectively expressed within the choroid plexus within the cerebral ventricles. By TGFB1. The disease is caused by variants affecting the gene represented in this entry. Belongs to the YIP1 family.