While the structural details of APS and SH2-B have been elegantly characterised by the Hubbard laboratory2,26,27, to date there have been no structural or biochemical studies of LNK, with only a single published example of the successful expression of any part of the LNK protein28 and no example of the yields and purity required for an in-depth structural and biochemical analysis. The gene discussed is SH2B3; the disease is autoimmune polyendocrinopathy.