Site-specific mutagenesis of human chorionic gonadotrophin (hCG)-beta subunit: influence of mutation on hCG production.
The heterodimeric glycoprotein hormones, human chorionic gonadotrophin (hCG), LH, TSH and FSH, consist of two non-covalently linked subunits, the alpha and beta subunits. The beta subunit is specific for each hormone and is responsible for the biological specificity, but the beta subunits of different hormones show some degree of structural homology. The CAGY (cysteine-alanine-glycine-tyrosine) region is one of the amino acid sequences that is homologous in different beta subunits and is highly conserved between species. In the present study, site-specific in-vitro mutagenesis was used to change three individual nucleotides in the centre of the CAGY region of the hCG-beta subunit, and the effects of these mutations on hCG production was determined by in-vitro transcription and then translation in Xenopus laevis oocytes. The results indicate that the CAGY region, particularly the glycine residue at position 36 in the beta subunit, is essential for the production of hCG. This finding is consistent with previous studies showing that this region is necessary for the biological activity of human TSH.
Azuma
C
C
Department of Obstetrics and Gynecology, Osaka University Medical School, Japan.
Miyai
K
K
Saji
F
F
Kamiura
S
S
Tokugawa
Y
Y
Kimura
T
T
Ohashi
K
K
Koyama
M
M
Iijima
Y
Y
Kashiwai
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D006063:Chorionic Gonadotropin / Q000096:biosynthesis / Q000235:genetics*; D018997:Chorionic Gonadotropin, beta Subunit, Human; D004247:DNA / Q000235:genetics; D004274:DNA, Recombinant; D005260:Female; D005786:Gene Expression Regulation; D015292:Glycoprotein Hormones, alpha Subunit / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D014982:Xenopus laevis
D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D004274:DNA, Recombinant; D015292:Glycoprotein Hormones, alpha Subunit; D010446:Peptide Fragments; D012333:RNA, Messenger; D004247:DNA