Members of this family adopt a structure consisting of an immunoglobulin-like beta-sandwich, with seven strands in two beta-sheets, in a Greek-key topology. They are required for binding to the cytokine Interleukin-6 [1].

1: Structure of the extracellular domains of the human interleukin-6 receptor alpha -chain. Varghese JN, Moritz RL, Lou MZ, Van Donkelaar A, Ji H, Ivancic N, Branson KM, Hall NE, Simpson RJ; Proc Natl Acad Sci U S A. 2002;99:15959-15964. PMID:12461182