Acts as a GTPase-activating protein (GAP) for SAR1 (PubMed:24947508). Contrary to its SEC23 homolog, NEL1 does not associate with SEC24 and its homologs, nor does it associate with the COPII components, suggesting that it is unlikely that NEL1 functions as a structural component of the vesicle coat machinery (PubMed:24947508). May function as a signaling molecule (PubMed:24947508). Is diffusely localized throughout the cytosol, and does not accumulate at ER exit sites (ERES). Leads to a significant growth defect in the temperature-sensitive SAR1-D32G mutant background. Present with 450 molecules/cell in log phase SD medium. Belongs to the SEC23/SEC24 family. SEC23 subfamily.