The complete amino acid sequences of beta-subunits of two distinct chum salmon GTHs.
The complete amino acid sequences of beta-subunits of chum salmon (Oncorhynchus keta) gonadotropin (GTH) I and GTH II were determined. Both GTH I beta and GTH II beta were treated with neuraminidase, and then reduced and carboxymethylated. Both of the modified subunits were digested separately with several endopeptidases. The resulting fragments were purified by reversed-phase high-performance liquid chromatography and subjected to sequence analysis by manual Edman degradation. GTH I beta was a single component consisting of 113 amino acid residues including 12 half-cystine residues. GTH II beta was composed of two variants, both of which consisted of 119 amino acid residues including 12 half-cystine residues and differed from each other by substitutions at only two amino acid residues. The presence of an N-linked glycosylation consensus sequence (Asn-X-Thr) in both GTH I beta and GTH II beta is also proved. GTH I beta has only a 31% sequence identity with GTH II beta and less than 40% with human LH beta and FSH beta, and differed from these beta-subunits in the disulfide alignments. It appeared that GTH II beta is almost identical to the molecule previously characterized as the beta-subunits of maturational GTH from chinook and carp, and more similar to human LH beta (48% identity) than to human FSH beta (38% identity). Thus, the elucidation of the complete amino acid sequences for GTH I beta and GTH II beta firmly establishes that the chum salmon pituitary gland secretes two chemically distinct molecules homologous to LH and FSH of the tetrapods.
Itoh
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H
Laboratory of Molecular Endocrinology, School of Fisheries Sciences, Kitasato University, Iwate, Japan.
Suzuki
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K
Kawauchi
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H
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D005260:Female; D006065:Gonadotropins, Pituitary; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D012474:Salmon; D013045:Species Specificity
D000596:Amino Acids; D006065:Gonadotropins, Pituitary; D010446:Peptide Fragments; C057763:gonadotropin- pituitary, beta-subunit I, salmon