The role of the carboxyl-terminal 6 amino acid extension of human TSH beta subunit.
The nucleotide sequence of human thyroid stimulating hormone (hTSH) gene can encode a protein of 138 amino acids. However, the mature polypeptide is lacking 6 amino acids of the carboxyl-terminus (C-terminus), suggesting posttranslational cleavage of these residues. To analyze a possible function of these 6 amino acids, we expressed two hTSH beta cDNAs with or without the 6 codons for C-terminal extension, together with alpha subunit cDNA in CHO cells, and determined the amino acid sequence of C-terminus of hTSH beta. hTSH beta propeptides without C-terminal extension were glycosylated, associated with alpha subunit and secreted, as normal propeptides were, and its heterodimer with alpha subunit showed normal TSH bioactivity in FRTL-5 bioassay. These data indicate that the 6 amino acid C-terminal extension is not necessary for the hTSH maturation in the process of the biosynthesis and for its bioactivity.
Takata
K
K
Institute for Molecular and Cellular Biology, Osaka University, Japan.
Watanabe
S
S
Hirono
M
M
Tamaki
M
M
Teraoka
H
H
Hayashizaki
Y
Y
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001681:Biological Assay; D002268:Carboxypeptidases / Q000378:metabolism; D043422:Carboxypeptidases A; D002460:Cell Line; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D004247:DNA / Q000235:genetics; D015870:Gene Expression; D006031:Glycosylation; D006801:Humans; D007163:Immunosorbent Techniques; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D011499:Protein Processing, Post-Translational; D051381:Rats; D013329:Structure-Activity Relationship; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism; D013972:Thyrotropin / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D014170:Transformation, Genetic
D046911:Macromolecular Substances; D010446:Peptide Fragments; D013972:Thyrotropin; D004247:DNA; D000242:Cyclic AMP; D002268:Carboxypeptidases; D043422:Carboxypeptidases A