Expression of biologically active fusion genes encoding the common alpha subunit and the follicle-stimulating hormone beta subunit. Role of a linker sequence.
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.
Sugahara
T
T
Department of Molecular Biology & Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Sato
A
A
Kudo
M
M
Ben-Menahem
D
D
Pixley
M R
MR
Hsueh
A J
AJ
Boime
I
I
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002478:Cells, Cultured; D003001:Cloning, Molecular; D006224:Cricetinae; D017931:DNA Primers; D005640:Follicle Stimulating Hormone / Q000235:genetics* / Q000378:metabolism; D037201:Follicle Stimulating Hormone, beta Subunit; D015292:Glycoprotein Hormones, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000235:genetics*
D017931:DNA Primers; D037201:Follicle Stimulating Hormone, beta Subunit; D015292:Glycoprotein Hormones, alpha Subunit; D011993:Recombinant Fusion Proteins; D005640:Follicle Stimulating Hormone