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The Biochemical journal1996; 320 ( Pt 1)(Pt 1); 137-143; doi: 10.1042/bj3200137

A 19 kDa protein secreted by the endometrium of the mare is a novel member of the lipocalin family.

Abstract: Large quantities of an unusual 19 kDa protein (p19) are secreted into the lumen of the uterus of the mare (Equus caballus) during the oestrous cycle and early pregnancy. p19 associates strongly with the acellular capsule that surrounds the young horse conceptus and is believed to be important in maintaining pregnancy. Here we report the complete cDNA sequence encoding p19, its expression patterns in horse tissues and a Southern blot analysis of the gene in horse DNA. The predicted amino acid sequence of the p19 cDNA demonstrated a signal peptide of 18 residues and a mature protein of 162 residues, giving a predicted molecular mass of 18.8 kDa for the secreted protein. Analysis of the predicted amino acid sequence showed that p19 belongs to the lipocalin family of proteins, which are classified on the basis of three conserved amino acid sequence motifs and an eight-stranded anti-parallel beta-barrel conformation. Overall, p19 was most similar to the mouse major urinary protein (MUP) lipocalins (30-34% identity). Secondary structural predictions and structural modelling using the MUP 1 crystal structure coordinates gave convincing evidence that the three-dimensional structure of p19 closely resembles that of the lipocalins. However, p19 has several unusual substitutions in one of the three conserved lipocalin motifs and therefore seems to be a novel member of the family. Lipocalins perform many different functions but most bind small hydrophobic molecules and the majority act as transport proteins. The function of p19 might therefore be as a carrier of a maternal factor needed to sustain the developing embryo during pregnancy, or it could be incorporated into the embryonic capsule and perform some other function. Northern blot analysis demonstrated that expression of p19 is confined to the endometrial lining of the mare's uterus, and hybridization studies in situ showed that the mRNA for p19 is localized to the glandular and luminal epithelia of the endometrium. A Southern blot analysis of horse DNA indicated a single gene for p19 that seems to be at least 4.5 kb in size.
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Publication Date: 1996-11-15 PubMed ID: 8947478PubMed Central: PMC1217908DOI: 10.1042/bj3200137Google Scholar: Lookup
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  • Journal Article
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  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses the discovery of a protein, named p19, secreted by the mare’s uterus during the oestrus cycle and early pregnancy. This protein, found to be part of the lipocalin family of proteins, may play an essential role in horse pregnancy by carrying maternal factors or forming part of the embryonic capsule.

Methodology and Protein Discovery

  • The researchers identified p19 protein as being abundantly secreted into the uterus of a mare during the oestrus cycle and early pregnancy phases. Through a complete cDNA sequence analysis, they found that p19 is a protein of 19 kilodaltons (kDa).
  • They determined that the protein was robustly binding to the acellular capsule, a non-cellular structure that envelops the young horse embryo. They hypothesized that it could play a significant role in sustaining horse pregnancies.

Protein Characteristic and Lipocalin Family

  • The protein was further characterized using the mare’s DNA and tissue samples. The data showed that p19 is a lipocalin family protein marked by three conserved amino acid sequence motifs and a specific conformation.
  • Lipocalin proteins perform various functions, the majority of them acting as transport proteins that bind to small hydrophobic molecules. Consequently, the researchers propose p19 might work as a carrier of a maternal factor necessary to sustain the embryo during the pregnancy or become part of the embryonic capsule playing a different role.
  • However, they also noted some unusual changes in one of the three conserved lipocalin motifs in p19, leading them to categorize it as a novel member of the lipocalin family.
  • The identified protein demonstrated its highest resemblance to the mouse MUP lipocalins, with 30-34% identity.

Gene Expression and Localization

  • Researchers found that p19’s expression was restricted to the endometrial lining of the mare’s uterus. They pinned the mRNA for p19 to the glandular and luminal epithelia of the endometrium using in situ hybridization studies.
  • Analysis of horse DNA using Southern blot techniques revealed a single gene for p19, estimated to be at least 4.5 kilobases (kb) in size.

In conclusion, this research provides valuable insights into a novel protein that might significantly influence horse pregnancies.

Cite This Article

APA
Crossett B, Allen WR, Stewart F. (1996). A 19 kDa protein secreted by the endometrium of the mare is a novel member of the lipocalin family. Biochem J, 320 ( Pt 1)(Pt 1), 137-143. https://doi.org/10.1042/bj3200137

Publication

The Biochemical journal
ISSN: 0264-6021
NlmUniqueID: 2984726R
Country: England
Language: English
Volume: 320 ( Pt 1)
Issue: Pt 1
Pages: 137-143

Researcher Affiliations

Crossett, B
  • T.B.A. Equine Fertility Unit, Department of Clinical Veterinary Medicine, University of Cambridge, U.K.
Allen, W R
    Stewart, F

      MeSH Terms

      • Amino Acid Sequence
      • Animals
      • Base Sequence
      • Blotting, Northern
      • Blotting, Southern
      • Carrier Proteins / genetics
      • Cloning, Molecular
      • DNA, Complementary
      • Endometrium / metabolism
      • Female
      • Horses
      • In Situ Hybridization
      • Lipocalins
      • Molecular Sequence Data
      • Pregnancy
      • Sequence Homology, Amino Acid

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