Structure of the human smoothened receptor bound to an antitumour agent.

The crystal structure of the human smoothened (SMO) receptor is presented in complex with a small-molecule antitumour agent; this represents the first example of a non-class-A, 7-transmembrane (7TM) receptor structure, revealing different conserved motifs common within class frizzled 7TM receptors and an unusually complex arrangement of long extracellular loops stabilized by disulphide bonds.