Is TALL-1 a trimer or a virus-like cluster?

Abstract
Native TALL-1 (B-cell activation factor, BAFF; also known as BlyS) was initially described as a homotrimer1,2,3, but Liu and colleagues claim that it is a 60-subunit complex4,5,6 on the basis of their results from X-ray crystallography and size-exclusion chromatography. They consider TALL-1 60-mers to be the biologically active form, and the arrangement of the 60-mers resembles that of the capsid of satellite tobacco necrosis virus4,5,6. Here we show that active TALL-1 is trimeric under normal physiological conditions and that formation of higher-order oligomers is an artefact of tagging the amino terminus of the protein with a histidine tag.