Nucleotide sequence of the cDNA encoding the precursor of the beta subunit of rat lutropin.

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Abstract
The nucleotide sequences of cDNA encoding the precursor of the .beta. subunit of rat lutropin, a polypeptide hormone that regulates gonadal function, including the development of gametes and the production of steroid sex hormones were determined. The c[complementary]DNA were prepared from poly(A)+ RNA derived from the pituitary glands of rats 4 wk after ovariectomy and were cloned in bacterial plasmids. Bacterial colonies containing transfected plasmids were screened by hybridization with a 32P-labeled cDNA encoding the .beta. subunit of human chorionic gonadotropin, a protein that is related in structure to lutropin. Several recombinant plasmids were detected that by nucleotide sequence analyses contained coding sequences for the precursor of the .beta. subunit of lutropin. Complete determination of the nucleotide sequences of these cDNA, and of cDNA reverse-transcribed from pituitary poly(A)+ RNA by using a synthetic pentadecanucleotide as a primer of RNA, provided the entire 141-codon sequence of the precursor of the .beta. subunit of rat lutropin. The precursor consists of a 20 amino acid leader (signal) peptide and an apoprotein of 121 amino acids. The amino acid sequence of the rat lutropin .beta. subunit shows similarity to the .beta. subunits of the ovine/bovine, porcine and human lutropins (81, 86 and 74% of amino acids identical, respectively). Blot hybridization of pituitary RNA separated by electrophoresis on agarose gels showed that the mRNA encoding the lutropin .beta. subunit consists of approximately 700 bases. The availability of cDNA for both the .alpha. and .beta. subunits of lutropin will facilitate studies of the regulation of lutropin expression.