Guanine nucleotide exchange factor for Rab-3A isoform 1, also known as RAB3IL, is a 382 amino acid protein that belongs to the SEC2 family. RAB3IL1 is a guanine nucleotide exchange factor (GEF) for Rab3A. RAB3IL1 competes for an interaction with Rab3A and IHPK1 through its coiled coil domain, which does not require IHPK1 kinase activity. Recombinant human RAB3IL1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.