Guanine nucleotide exchange factor (GEF) which may activate RAB6A and RAB39A and/or RAB39B. Promotes the exchange of GDP to GTP, converting inactive GDP-bound Rab proteins into their active GTP-bound form. Involved in the negative regulation of neurite outgrowth (By similarity). Interacts with RAB6A bound to GTP. The disease is caused by variants affecting the gene represented in this entry. Belongs to the RAB6IP1 family. Extended N-terminus. Truncated N-terminus.