Plays a role in the organization of the endoplasmic reticulum exit sites (ERES), also known as transitional endoplasmic reticulum (tER) (PubMed:21478858). In association with tfg-1, accumulates at ERES to positively regulate secretory cargo trafficking from the endoplasmic reticulum to the endoplasmic reticulum-Golgi intermediate compartment (ERGIC) and Golgi apparatus (PubMed:21478858). Interacts with tfg-1 (via N-terminus); the interaction is direct and is required for both the localization of tfg-1 and to maintain the distribution of sec-16A.1 at endoplasmic reticulum exit sites (ERES). Co-localizes with tfg-1 at endoplasmic reticulum exit sites (ERES). RNAi-mediated knockdown abolishes localization of tfg-1 to endoplasmic reticulum exit sites (ERES). Belongs to the SEC16 family.