Human secreted B7-H4, also known as B7x and B7S1, with C-terminal His-Avi-Tags. GenBank Accession No. NM_078902, a.a 29-258 expressed in a HEK293 cell expression system and enzymatically biotin-labeled using Avi-tag™ technology. MW = 28.6 kDa (monomer). This protein runs at a higher M.W. by SDS PAGE due to glycosylation.