Porcine Luteinizing Hormone and its Subunits.

A new method is described for the isolation of the subunits of porcine luteinizing hormone which have not been characterized before. By chromatography on SE-Sephadex C-25 in 8 M urea, the two subunits LHα and β were obtained in good yield and without apparent cross contamination. The physicochemical and immunological properties of these subunits were studied. Unlike the bovine or ovine LHβ subunits described earlier, porcine LHβ subunit does not contain lysine. Porcine LHα subunit is electrophoretically heterogeneous and two components represented by two homogeneous electrophoretical zones were isolated and characterized. The amino acid composition of these components is very similar; they differ, however, slightly in peptide maps of their tryptic digests. Whole LHα subunit was submitted to specific cleavage at methionine residues by cyanogen bromide and a homogeneous peptide not containing homoserine was isolated. The latter represents most probably the C-terminal fragment of LHα subunit. Its partial amino-acid sequence and composition is: Gly-Asn-Ala-Arg-Val-Glu-(His3,Lys,CM-Cys3-4,Asp,Thr2,Ser,Glu,Tyr2)-Ser. The fragment contains 34% of sugar (by weight). In view of the similarity in peptide maps and the unambiguous sequence described above, the primary structure of the different components of LHα subunit must be very similar. [ABSTRACT FROM AUTHOR]