PARTIAL SEQUENCING AND IDENTIFICATION OF 3 PROTEINS FROM EQUINE UTERINE SECRETION REGULATED BY PROGESTERONE

This study describes three proteins that are regulated by progesterone in their production and release into the uterine secretion of mares. The proteins appear as predominant fractions in the uterine secretion during the luteal phase of the cycle. Ovariectomized mares do not rele ase these proteins in considerable amounts; however, progesterone repl acement strongly stimulates the production of these proteins. SDS-PAGE and blotting onto polyvinylidendifluoride membrane revealed the possi bility of partial amino-acid sequencing of these three molecules. One protein was identified as equine uteroglobin (< 6.5 kDa), another as a n equine phospholipase A2 (17.0 kDa), and the third sequence Leu-X-Met -Gly-Pro -Gly-Asp-Pro-Asn-Phe-Asp-Glu-Lys-Leu-Val-Lys- Ser-Val-Ala-Leu -Ala-Ser-Asn could not be identified in the databases checked for such sequence homology. This protein was isolated from a strong band of SD S-PAGE migrating at 22.0 kDa.