The crystal structure of the β subunit of luteinizing hormone and a model for the intact hormone

The beta subunit of bovine luteinizing hormone (LH) was crystallized and its structure solved to 3.15 angstrom resolution by molecular replacement using human chorionic gonadotropin (hCG) beta subunit as search model. The asymmetric unit contains two copies of the beta subunit that are related by a non-crystallographic symmetry (NCS) two-fold axis, both copies of which contain proteolytic cleavages after amino acid 100. It is noteworthy that the oligosaccharide moieties covalently attached at asparagine 13 were particularly pronounced in the electron density, allowing seven sugar residues to be defined. The alpha subunit of LH, which is common to all glycosylated gonadotropin hormones, was placed by superposition of hCG on the LH beta subunits, thereby yielding a model for the intact hormone.