Nucleotide exchange factor, also known as SIL1, is a resident endoplasmic reticulum (ER), N-linked glycoprotein with an N-terminal ER targeting sequence, 2 putative N-glycosylation sites, and a C-terminal ER retention signal. This protein functions as a nucleotide exchange factor for another unfolded protein response protein. Mutations in this gene have been associated with Marinesco-Sjogren syndrome. Recombinant human SIL1 protein, fused to His-tag at C-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.