Comparison of bovine and mouse pituitary glycoprotein hormone pre-alpha subunits synthesized in vitro.
Poly(A)-containing RNA isolated from bovine and mouse pituitaries and a mouse pituitary thyrotropic tumor was translated in a wheat germ cell-free biosynthetic system. A precursor of the glycoprotein hormone alpha subunit, "pre-alpha," was immunoprecipitated from the translation mixtures with antiserum against bovine luteinizing hormone (LH; lutropin) alpha. The specificity of the immunoprecipitation was shown by competition with authentic bovine LHalpha and lack of competition with bovine thyroid-stimulating hormone (TSH; thyrotropin) beta. Bovine and mouse pre-alpha subunits migrated identically in sodium dodecyl sulfate gradient polyacrylamide slab gels with an apparent molecular weight of about 17,000. Pre-alpha comprised 2-3% and 20-30% of the total proteins translated with pituitary and pituitary tumor mRNA, respectively. Microanalysis of amino acid sequence of the pre-alpha subunits containing various radiolabeled amino acids gave the following partial sequence for mouse tumor pre-alpha: [Formula: see text] Met was also found in positions 1, 14, and 17 in mouse pituitary pre-alpha but only in residue 1 of the bovine pituitary pre-alpha subunit. Leu was found in identical positions in bovine pituitary pre-alpha, with an additional Leu in position 17. Leu in the common positions (12, 15, 19, and 22) has also been found in human choriogonadotropin pre-alpha subunit [Birken, S., Fetherston, J., Desmond, J., Canfield, R. & Boime, I. (1978) Biochem. Biophys. Res. Commun. 85, 1247-1253]. The data demonstrate that pituitary as well as placental glycoprotein hormone alpha subunits are synthesized with an amino-terminal hydrophobic extension, in accord with the "signal hypothesis" for secreted proteins. Furthermore, the positions of the hydrophobic amino acid Leu have been strictly conserved in pre-alpha subunits from various species and in two different tissues, the pituitary and placenta.
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D006023:Glycoproteins / Q000096:biosynthesis*; D007700:Kinetics; D007986:Luteinizing Hormone / Q000096:biosynthesis*; D009374:Neoplasms, Experimental / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000378:metabolism*; D010944:Plants / Q000378:metabolism; D011061:Poly A / Q000378:metabolism; D014176:Protein Biosynthesis; D013045:Species Specificity; D013972:Thyrotropin / Q000096:biosynthesis*; D014908:Triticum / Q000378:metabolism
D006023:Glycoproteins; D011061:Poly A; D007986:Luteinizing Hormone; D013972:Thyrotropin