Purification and characterization of the rat ovarian receptor for luteinizing hormone. Structural studies of subunit interaction.

We have purified the luteinizing hormone (LH)/human choriogonadotropin (hCG) receptor by sequential affinity column on wheat germ lectin-Sepharose and hCG-Sepharose. The method was designed to allow also the purification of lactogen receptor from the initial starting material. The purified LH/hCG receptor retained full binding affinity and was identified as a single protein of Mr = 73,000 +/- 3,000 on sodium dodecyl sulfate-gel electrophoresis. Cross-linking studies performed after binding of hCG to the purified LH/hCG receptor indicated that the hCG alpha-subunit undergoes predominant interaction with the receptor molecule. The influence of the beta-subunit in this interaction seems to occur mainly through its association with the alpha-subunit, presumably by conferring specificity to the alpha-subunit for its hormonal interaction with the receptor. The technique described in this study is simple and allows rapid purification of microgram amounts of biologically active receptor suitable for further molecular characterization, microsequencing, and functional reconstitution studies.