Journal of Clinical Endocrinology & Metabolism, Vol 65, 1067-1071, Copyright © 1987 by Endocrine Society

ARTICLES

Pregnancy-associated endometrial alpha 2-globulin, the major secretory protein of the luteal phase and first trimester pregnancy endometrium, is not glycosylated prolactin but related to beta-lactoglobulins

SC Bell, JW Keyte and GT Waites
Department of Biochemistry, University of Leicester, United Kingdom.

We previously reported that the major secretory protein of the endometrium during the first trimester of pregnancy, pregnancy- associated endometrial alpha 2-globulin (alpha 2-PEG), also represented the major secretory protein during the mid- to late luteal phase. Recently, the major secretory endometrial protein during the luteal phase of the menstrual cycle was identified as glycosylated PRL (G- PRL). Although certain properties of alpha 2-PEG resemble G-PRL, in this study G-PRL was demonstrated to be immunochemically distinct from alpha 2-PEG, and deglycosylation of alpha 2-PEG produced a protein unrelated to PRL. The sequence of the 38 N-terminal amnio acid residues of alpha 2-PEG was determined by a gas phase sequenator. A sequence of Met-Asp-Ileu-Pro-Gln-Thr-Lys-Gln-Asp-Leu-Glu-Leu-Pro-Lys-Leu-Ala-G ly- Lys-Trp- His-Ser-Met-Ala-Met-Ala-Thr-Asn-?-Ileu-Ser-Leu-Met-Ala-Thr-Leu- Lys -Ala-Pro was obtained which was unique and unrelated to that of PRL. However, sequence homology between alpha 2-PEG and the major milk whey protein beta-lactoglobulin of the horse was demonstrated. The data indicate that alpha 2-PEG is a unique protein and is a human homolog of the beta-lactoglobulin family.

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