Mouse secreted CD137, also known as Tumor Necrosis Factor Receptor Superfamily member 9, TNFRSF9, and ILA, GenBank Accession No. NM_001561, a.a. 24-187, fused at the Cterminus to the Fc portion of mouse IgG2a, with a C-terminal AviTag^TM expressed in a HEK293 cell expression system. MW = 46.7 kDa (monomer). This protein runs at a higher MW by SDSPAGE due to glycosylation.