• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of biochemjBJ Latest papers and much more!
Biochem J. Nov 15, 1996; 320(Pt 1): 137–143.
PMCID: PMC1217908

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.

Full Text

The Full Text of this article is available as a PDF (550K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Samuel CA, Allen WR, Steven DH. Studies on the equine placenta. I. Development of the microcotyledons. J Reprod Fertil. 1974 Dec;41(2):441–445. [PubMed]
  • Betteridge KJ, Eaglesome MD, Mitchell D, Flood PF, Beriault R. Development of horse embryos up to twenty two days after ovulation: observations on fresh specimens. J Anat. 1982 Aug;135(Pt 1):191–209. [PMC free article] [PubMed]
  • Oriol JG, Sharom FJ, Betteridge KJ. Developmentally regulated changes in the glycoproteins of the equine embryonic capsule. J Reprod Fertil. 1993 Nov;99(2):653–664. [PubMed]
  • Oriol JG, Betteridge KJ, Clarke AJ, Sharom FJ. Mucin-like glycoproteins in the equine embryonic capsule. Mol Reprod Dev. 1993 Mar;34(3):255–265. [PubMed]
  • Zavy MT, Sharp DC, Bazer FW, Fazleabas A, Sessions F, Roberts RM. Identification of stage-specific and hormonally induced polypeptides in the uterine protein secretions of the mare during the oestrous cycle and pregnancy. J Reprod Fertil. 1982 Jan;64(1):199–207. [PubMed]
  • Stewart F, Charleston B, Crossett B, Barker PJ, Allen WR. A novel uterine protein that associates with the embryonic capsule in equids. J Reprod Fertil. 1995 Sep;105(1):65–70. [PubMed]
  • Allen WR, Mathias S, Lennard SN, Greenwood RE. Serial measurement of peripheral oestrogen and progesterone concentrations in oestrous mares to determine optimum mating time and diagnose ovulation. Equine Vet J. 1995 Nov;27(6):460–464. [PubMed]
  • Ricketts SW. The technique and clinical appication of endometrial biopsy in the mare. Equine Vet J. 1975 Apr;7(2):102–108. [PubMed]
  • Chomczynski P, Sacchi N. Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. Anal Biochem. 1987 Apr;162(1):156–159. [PubMed]
  • Feinberg AP, Vogelstein B. A technique for radiolabeling DNA restriction endonuclease fragments to high specific activity. Anal Biochem. 1983 Jul 1;132(1):6–13. [PubMed]
  • Short JM, Sorge JA. In vivo excision properties of bacteriophage lambda ZAP expression vectors. Methods Enzymol. 1992;216:495–508. [PubMed]
  • Altschul SF, Gish W, Miller W, Myers EW, Lipman DJ. Basic local alignment search tool. J Mol Biol. 1990 Oct 5;215(3):403–410. [PubMed]
  • Attwood TK, Beck ME, Bleasby AJ, Parry-Smith DJ. PRINTS--a database of protein motif fingerprints. Nucleic Acids Res. 1994 Sep;22(17):3590–3596. [PMC free article] [PubMed]
  • Flower DR, North AC, Attwood TK. Structure and sequence relationships in the lipocalins and related proteins. Protein Sci. 1993 May;2(5):753–761. [PMC free article] [PubMed]
  • Flower DR. Multiple molecular recognition properties of the lipocalin protein family. J Mol Recognit. 1995 May-Jun;8(3):185–195. [PubMed]
  • Flower DR, Sansom CE, Beck ME, Attwood TK. The first prokaryotic lipocalins. Trends Biochem Sci. 1995 Dec;20(12):498–499. [PubMed]
  • Rost B, Sander C. Prediction of protein secondary structure at better than 70% accuracy. J Mol Biol. 1993 Jul 20;232(2):584–599. [PubMed]
  • Böcskei Z, Groom CR, Flower DR, Wright CE, Phillips SE, Cavaggioni A, Findlay JB, North AC. Pheromone binding to two rodent urinary proteins revealed by X-ray crystallography. Nature. 1992 Nov 12;360(6400):186–188. [PubMed]
  • Sander C, Schneider R. Database of homology-derived protein structures and the structural meaning of sequence alignment. Proteins. 1991;9(1):56–68. [PubMed]
  • Pervaiz S, Brew K. Homology of beta-lactoglobulin, serum retinol-binding protein, and protein HC. Science. 1985 Apr 19;228(4697):335–337. [PubMed]
  • Flower DR. The lipocalin protein family: a role in cell regulation. FEBS Lett. 1994 Oct 31;354(1):7–11. [PubMed]
  • McDowell KJ, Adams MH, Franklin KM, Baker CB. Changes in equine endometrial retinol-binding protein RNA during the estrous cycle and early pregnancy and with exogenous steroids. Biol Reprod. 1995 Feb;52(2):438–443. [PubMed]
  • Bohn H, Kraus W, Winckler W. New soluble placental tissue proteins: their isolation, characterization, localization and quantification. Placenta Suppl. 1982;4:67–81. [PubMed]
  • Julkunen M, Koistinen R, Suikkari AM, Seppälä M, Jänne OA. Identification by hybridization histochemistry of human endometrial cells expressing mRNAs encoding a uterine beta-lactoglobulin homologue and insulin-like growth factor-binding protein-1. Mol Endocrinol. 1990 May;4(5):700–707. [PubMed]
  • Julkunen M, Koistinen R, Sjöberg J, Rutanen EM, Wahlström T, Seppälä M. Secretory endometrium synthesizes placental protein 14. Endocrinology. 1986 May;118(5):1782–1786. [PubMed]
  • Seppälä M, Riittinen L, Julkunen M, Koistinen R, Wahlström T, Iino K, Alfthan H, Stenman UH, Huhtala ML. Structural studies, localization in tissue and clinical aspects of human endometrial proteins. J Reprod Fertil Suppl. 1988;36:127–141. [PubMed]
  • Igarashi M, Nagata A, Toh H, Urade Y, Hayaishi O. Structural organization of the gene for prostaglandin D synthase in the rat brain. Proc Natl Acad Sci U S A. 1992 Jun 15;89(12):5376–5380. [PMC free article] [PubMed]

Articles from Biochemical Journal are provided here courtesy of The Biochemical Society

Formats:

Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...

Links

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...