Background：Guanine nucleotide exchange factor that specifically activates the small GTPase SAR1B. Mediates the recruitement of SAR1B and other COPII coat components to endoplasmic reticulum membranes and is therefore required for the formation of COPII transport vesicles from the ER.
Was first identified based on its probable role in the regulation of pituitary gene transcription. Binds to the prolactin gene(PRL) promoter and seems to activate transcription.
