Isolation and identification of porcine embryonic basic protein as a fragment of pregnancy-associated glycoprotein-2.
Between days 11 and 12 of gestation, the porcine conceptus undergoes a metamorphosis from a spherical blastocyst to an elongate thread-like form. During this process, the conceptus secretes a variety of products. One of these products is protein previously referred to as porcine embryonic basic protein (BP). This protein has been shown to be a major secreted product between days 13 and 18. In this study, we report a simple two-step procedure to isolate BP from day 15 porcine conceptus conditioned medium, utilized ion-exchange chromatography and reverse-phase HPLC. Purified BP was subjected to Edman degradation amino-terminal sequencing and a 25 amino acid residue sequence was obtained. Comparing the N-terminal sequence of BP to sequences in the GenBank database determined that BP shared amino acid homology with porcine pregnancy-associated glycoprotein-2 (PAG-2). The region of identity corresponded to an internal site of PAG-2, suggesting BP was a proteolytic fragment of PAG-2. The purified protein was confirmed to be BP by Western blot using a previously characterized anti-BP antiserum. Also, the BP was immunolocalized with the trophectoderm of day 11 blastocysts. Staining intensity was diminished in spherical blastocysts compared to elongated blastocysts. Although the function of PAG-2 and its cleavage product BP are unknown, the large quantity produced by the porcine conceptus and its sequence conservation across species may indicate a necessary role in early pregnancy.
Doré
J J
JJ
Department of Animal Science, University of Tennessee, Knoxville 37901, USA.
Kattesh
H G
HG
Godkin
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001755:Blastocyst / Q000378:metabolism; D017077:Culture Media, Conditioned; D005260:Female; D005865:Gestational Age; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013552:Swine
D017077:Culture Media, Conditioned; D010446:Peptide Fragments; D011257:Pregnancy Proteins; D016282:Aspartic Acid Endopeptidases; C094766:pregnancy-associated glycoprotein 1; C095584:pregnancy-associated glycoprotein 2