Preparation and properties of luteinizing hormone (LH) subunits from the turkey ( Meleagris gallopavo) and their recombination with subunits of ovine LH

Abstract

Subunits of turkey luteinizing hormone (LH) were prepared from highly purified turkey LH by countercurrent distribution (CCD) and Sephadex G-100 chromatography. The material with the low partition coefficient was designated turkey LH-α and that with the high partition coefficient was designated turkey LH-β. The LH-α eluted from Sephadex G-100 with a Ve Vo ratio of 2.41, while the LH-β eluted at 2.33. The α-subunit had more lysine than arginine, the reverse is seen in the LH-β. The β-subunit has a higher content of leucine, proline, valine, and glycine than the α, but appears to contain no methionine and probably no histidine. Both subunits are high in half-cystine residues. The bulk of the carbohydrate was associated with LH-α (14.9%), while the LH-β had a low carbohydrate content (4.4%). The isolated subunits had very low immuno- and bioactivity, but activity in radioimmunoand radioreceptor assays was regenerated by coincubation of the turkey subunits. Hybridization of turkey LH subunits with those from ovine LH also generated radioreceptor activity. The hybrid prepared with ovine LH-α and turkey LH-β was quite active in an avian testes radioreceptor assay; the reciprocal recombinant was not. The recombinant formed by turkey LH-α and ovine LH-β was active in a mammalian radioreceptor assay. The recombinant formed from turkey LH-α and ovine LH-β was quite active in a Leydig cell testosterone production assay, the reciprocal recombinant was not. Turkey LH is thus shown to be made up of two dissimilar subunits, each of which has substantial chemical homology with those from ovine LH. The species specificity of these two tetropod luteinizing hormones appears to be associated with the β-subunit.