Expression of biologically active fusion genes encoding the common alpha subunit and the follicle-stimulating hormone beta subunit. Role of a linker sequence

• Published in: The Journal of biological chemistry Vol. 271; no. 18; pp. 10445 - 10448
• Main Authors: Sugahara, T, Sato, A, Kudo, M, Ben-Menahem, D, Pixley, M R, Hsueh, A J, Boime, I
• Format: Journal Article
• Language: English
• Published: United States 03.05.1996
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Cells, Cultured; CHO Cells; Cloning, Molecular; Cricetinae; DNA Primers; Follicle Stimulating Hormone - genetics; Follicle Stimulating Hormone - metabolism; Follicle Stimulating Hormone, beta Subunit; Glycoprotein Hormones, alpha Subunit - genetics; Glycoprotein Hormones, alpha Subunit - metabolism; Humans; Molecular Sequence Data; Recombinant Fusion Proteins - genetics
• ISSN: 0021-9258
• DOI: 10.1074/jbc.271.18.10445

The gonadotropin/thyrotropin hormone family is characterized by a heterodimeric structure composed of a common alpha subunit noncovalently linked to a hormone-specific beta subunit. The conformation of the heterodimer is essential for controlling secretion, hormone-specific post-translational modifications, and signal transduction. Structure-function studies of follicle-stimulating hormone (FSH) and the other glycoprotein hormones are often hampered by mutagenesis-induced defects in subunit combination. Thus, the ability to overcome the limitation of subunit assembly would expand the range of structure-activity relationships that can be performed on these hormones. Here we converted the FSH heterodimer to a single chain by genetically fusing the carboxyl end of the FSH beta subunit to the amino end of the alpha subunit in the presence or absence of a linker sequence. In the absence of the CTP linker, the secretion rate was decreased over 3-fold. Unexpectedly, however, receptor binding/signal transduction was unaffected by the absence of the linker. These data show that the single-chain FSH was secreted efficiently and is biologically active and that the conformation determinants required for secretion and biologic activity are not the same.