Apoptosis regulatory protein Siva isoform 1, also known as SIVA1, is a death domain-containing proapoptotic protein identified as an intracellular ligand of CD27 and of the glucocorticoid-induced TNFR family-related gene, which are two members of the TNFR family expressed on lymphoid cells. SIVA1 expression is up-regulated in multiple pathological processes, little is known about the signaling pathway underlying the Siva-induced apoptosis. Recombinant human SIVA1 protein, fused to His-tag at N-terminus, was expressed in E.coli. (denatured)