Crystallization of ovine placental lactogen in a 1 : 2 complex with the extracellular domain of the rat prolactin receptor

Growth hormone and prolactin control somato-lactogenic biology. While high- resolution crystal structures have been determined for receptor complexes o f human growth hormone, no such information exists for prolactin. A stable 1:2 complex was formed between ovine placental lactogen, a close prolactin homologue, and two copies of the extracellular portion of the rat prolactin receptor. Using synchrotron radiation, native data have been collected to 2.3 Angstrom. Crystals contain one complex per asymmetric unit. The crystal structure of this complex will shed light on the structural reasons for cr oss-reactivity and specificity among the endocrine hormones, placental lact ogen, prolactin and growth hormone.