Partial cDNA sequence for the donkey chorionic gonadotrophin-beta subunit suggests evolution from an ancestral LH-beta gene.
Abstract: A 246 bp cDNA clone representing the C-terminal region of the donkey (Equus asinus) chorionic gonadotrophin (CG)-beta subunit was isolated from a placental library. The transcript contained the 3' untranslated region and 42% of the CG-beta subunit coding region (amino acid residues 85-146 of the mature peptide). Comparison of the deduced donkey amino acid sequence with the published horse CG-beta subunit protein sequence (where they overlapped) revealed an overall homology of 61%. However, most of the differences were in the C-terminal extension, which is thought not to be important for gonadotrophic activity, and appeared to be due to two nucleotide insertions in the donkey sequence (compared with a deduced horse nucleotide sequence) leading to a reading-frame shift. Amino acid homology in the disulphide 'core' region was 81%. Some of the differences in this region were in the 'determinant loop' (residues 93-100) and these are interpreted in relation to the observed biological activities of horse and donkey CG. The deduced amino acid sequence of the donkey cDNA indicated that it was larger than the majority of gonadotrophin-beta subunits due to a C-terminal extension. Primate and horse CG (and horse LH) beta subunits have analogous C-terminal extensions. The extension in the donkey subunit is 25 amino acid residues in length, compared with 28 in the horse and 24 in man. Comparisons with other available subunit DNA sequences indicated that, like the human CG-beta gene, the donkey gene probably evolved from an ancestral LH-like beta gene, following nucleotide deletions that allowed readthrough into previously untranslated DNA.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1990-04-01 PubMed ID: 2344391DOI: 10.1677/jme.0.0040143Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research discusses the isolation and examination of a cDNA clone for the donkey chorionic gonadotrophin-beta subunit, from which the researchers draw conclusions about its evolution from an ancestral LH-beta gene.
Introduction & Methodology
- The study revolves around a cDNA clone representing a region of the donkey chorionic gonadotrophin (GC)-beta subunit. This clone, containing about 42% of the subunit coding region, was isolated from a donkey’s placental library.
- The researchers focused on the C-terminal region of the GC-beta subunit, which contains a portion of the mature peptide’s amino acid sequence. They encoded 246 base pairs of this region.
Findings
- Comparative analysis between the donkey’s derived amino acid sequence and that of the horse’s published CG-beta subunit sequence showed an overall homology (similarity in structure) of 61% in overlapping areas.
- Most differences between the two sequences are found in the C-terminal extension, which is not considered essential for gonadotrophic activity.
- These differences are mainly due to two nucleotide insertions in the donkey sequence that cause a reading-frame shift.
- In the disulphide ‘core’ region, their amino acid homology is more consistent, reaching 81%. Certain discrepancies in this region are in the ‘determinant loop’ and relate to the differing biological activities of horse and donkey CG.
- The donkey’s cDNA sequence was found to be larger than most gonadotrophin-beta subunits. This size difference is due to a C-terminal extension – a feature also present in primate and horse CG (and horse LH) beta subunits. The donkey subunit’s extension is 25 amino acids long, as opposed to 28 in the horse and 24 in humans.
Conclusions
- The comparisons of the donkey subunit with other available subunit DNA sequences indicate that it likely evolved from an ancestral luteinizing hormone (LH) beta gene.
- This evolution resulted from nucleotide deletions that permitted read-through into previously untranslated DNA, similar to the evolution of the human CG-beta gene.
Cite This Article
APA
Leigh SE, Stewart F.
(1990).
Partial cDNA sequence for the donkey chorionic gonadotrophin-beta subunit suggests evolution from an ancestral LH-beta gene.
J Mol Endocrinol, 4(2), 143-150.
https://doi.org/10.1677/jme.0.0040143 Publication
Researcher Affiliations
- Thoroughbred Breeders' Association, Equine Fertility Unit, Mertoun Paddocks, Newmarket, Suffolk.
MeSH Terms
- Amino Acid Sequence
- Animals
- Base Sequence
- Biological Evolution
- Blotting, Northern
- Chorionic Gonadotropin / genetics
- DNA / genetics
- Female
- Humans
- Luteinizing Hormone / genetics
- Molecular Sequence Data
- Perissodactyla / genetics
- Placenta / metabolism
- RNA, Messenger / analysis
- Sequence Homology, Nucleic Acid
Citations
This article has been cited 2 times.- . New nucleotide sequence data on the EMBL File Server. Nucleic Acids Res 1991 Jan 11;19(1):201-5.
- Iles RK. The danger of studying human chorionic gonadotrophin action or expression in animal models. Br J Cancer 1991 May;63(5):827.
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