Human placental protein-14 (PP-14), a member of the lipocalin superfamily,
shares homology at the level of the primary and secondary structures with b
ovine beta-lactoglobulin. It is the most prominent endometrial protein synt
hesized by the glandular cells of endometrium under estrogen priming and pr
ogesterone stimulation. The temporal and spatial expression of PP-14 in the
female reproductive tract combined with its biological activities ex vivo
suggest that this glycoprotein probably plays an essential physiological ro
le in the regulation of fertilization, implantation, and maintenance of pre
gnancy. We proposed to elucidate the molecular mechanisms involved in the f
unction of this protein. A prerequisite to such investigations on any prote
in is the availability of sufficient amounts of the same in a homogenous fo
rm. Therefore, recombinant DNA technology was employed. The PP-14 cDNA was
obtained from the first-trimester endometrial tissue RNA by RT-PCR using un
ique primers. After confirming the identity of the gene, the protein was ex
pressed in Escherichia coli and purified to homogeneity. The gene was also
cloned and expressed in Pichia pastoris to obtain the protein product in a
glycosylated form. The recombinant proteins were immunocharacterized using
a cross-reactive antibody raised to bovine beta-lactoglobulin. Polyclonal a
ntiserum raised to the E coli expressed PP-14 also bound to the native PP-1
4 from amniotic fluid suggesting that recombinant PP-14 may be exploited to
elucidate functional aspects of the protein. (C) 1998 Academic Press.