Isolation and Nucleotide Sequence Analysis of a Cloned cDNA Encoding the β-Subunit of Bovine Follicle-Stimulating Hormone

Two different cDNAs containing sequences coding for the β-subunit of bovine follicle stimulating hormone (FSH-β) have been isolated from a phage lambda gt11 bovine pituitary cDNA library. The complete nucleotide sequence of both clones was determined, and the combined sequence represents most of FSH-β mRNA. The combined sequence contains 46 nucleotides of 5′-untranslated sequence followed by 387 nucleotides of coding sequence. The coding sequence predicts a 19-amino-acid amino-terminal precursor segment followed by the 110-amino-acid sequence of mature bovine FSH-β. The cDNA sequence demonstrates the presence of a long 3′-untranslated region containing 1295 bases followed by a segment representing the poly(A) portion of the mRNA. Thus, the combined sequence of the cDNAs suggests a minimal size of 1.7 kb for FSH-β mRNA. Analysis of FSH-β sequences present in bovine pituitary mRNA demonstrated the presence of an mRNA with a size of about 2.0 kb. This apparent discrepancy is probably due to the presence of a several-hundred nucleotide tract of poly(A) at the 3′ terminus of the mRNA. Comparison of the amino acid sequence predicted from the cDNA with the known amino acid sequence of the β-subunit of FSH from several different species demonstrates that the protein has been highly conserved.