Characterization of urokinase-type plasminogen activator of rat decidual tissue

Urokinase-type plasminogen activator (uPA) from artificially induced decidual tissue of rat has been purified to homogeneity employing chromatographic techniques and the final preparation has a specific activity of 12,084 I.U./mg. The purified preparation resolves into a single band following SDS-PAGE and has an apparent molecular weight of 45 kDa. HPLC of the purified fraction also yields a single peak at 45 kDa. Decidual uPA is immunogenic in rabbit and a monospecific antiserum raised against it does not cross react with human melanoma tPA or rat Yoshida sarcoma tPA but elicits a precipitin reaction with human uPA and extracts of rat placenta and kidney. The enzyme has a pH optimum of 7.5, a kM of 1.0 microM, is heat stable upto ten minutes at 42 degrees C and inhibited by anti-uPA IgG.

Use of metal-chelate affinity chromatography and hydrophobic interaction chromatography for purification of placental protein 12

Placental protein 12 was isolated from amniotic fluid. Albumin was removed by means of ion-exchange chromatography on DEAE-Sepharose and chromatography on Blue-Sepharose. Complete purification was obtained by metal-chelate affinity chromatography and hydrophobic interaction chromatography under mild conditions for desorption. Using this procedure large quantities of a highly purified preparation can be obtained in one run.

Binding of transforming growth factor-beta (TGF-beta) to pregnancy zone protein (PZP). Comparison to the TGF-beta-alpha 2-macroglobulin interaction

Pregnancy zone protein (PZP) is quantitatively the most important pregnancy-associated plasma protein and it has strong similarity to alpha 2-macroglobulin. Since alpha 2-macroglobulin is a binding protein for transforming growth factors-beta (TGF-beta), it was of interest to test whether the related protein, PZP, also binds to these growth-regulatory proteins. Using affinity-labelling methods, we demonstrate that PZP binds both TGF-beta 1 and TGF-beta 2 and that the binding characteristics are similar to those of the TGF-beta-alpha 2-macroglobulin interaction. TGF-beta 2 and TGF-beta 1 bind to PZP in a predominantly noncovalent manner in vitro. TGF-beta 1 and TGF-beta 2 bind to both the dimeric and tetrameric forms of PZP. Our studies also indicate that PZP binds TGF-beta 2 with higher affinity than TGF-beta 1. Finally, we demonstrate that PZP inhibits the binding of TGF-beta 1 and TGF-beta 2 to their cell surface receptors. The increased level of PZP during pregnancy may affect the action of TGF-beta by regulating the distribution, clearance and/or general availability of TGF-beta. The preferential binding of TGF-beta 2 over TGF-beta 1 by PZP implies that PZP may differentially regulate the action of TGF-beta 1 and TGF-beta 2.

Human decidua-associated protein hDP200 appears to be a rheumatoid factor

The amino acid sequences of the amino-terminal of the two different polypeptide chains of the human decidua-associated protein hDP200, with apparent molecular masses of 55 and 25 kDa, were determined. The amino-terminal sequence of the 55 kDa chain revealed that it is an immunoglobulin heavy chain, of the VH-III subgroup and the amino-terminal sequence of the 25 kDa chain showed that it is a human kappa V-III light chain. The sequence data indicate that hDP200 is an immunoglobulin. The ability of the hDP200 molecules to form high molecular weight complexes with immunoglobulins of other classes suggest that hDP200 is a rheumatoid factor.

Purification and characterization of phosphatidylinositol synthase from human placenta

Phosphatidylinositol synthase (CDP-1,2-diacyl-sn-glycerol:myoinositol 3-phosphatidyltransferase, EC 2.7.8.11) was purified from the microsomal fraction of human placenta. The Triton X-100-extracted enzyme was purified 8300-fold over the microsomal fraction by affinity chromatography on CDP-diacylglycerol-Sepharose followed by ion-exchange chromatography on Mono Q. The purified enzyme had a molecular mass of 24,000 Da on SDS/PAGE. The enzyme had a pH optimum at 9.0, required Mn2+ or Mg2+, and was inhibited by Ca2+ and Zn2+. The Km for myo-inositol was determined to be 0.28 mM. Optimal activity was obtained at 0.2-0.4 mM CDP-diacylglycerol; higher concentrations of the lipid substrate inhibited the enzyme reaction. The enzyme was inhibited by nucleoside di- and tri-phosphates, Pi and PPi. CDP competitively inhibited the enzyme reaction with a Kis of 4 mM. The optimal temperature for the PtdIns synthase reaction was 50 degrees C.

[Molecules of the family of aspartic proteinases in the placenta of ruminants: hormones or proteins?]

The ruminant placenta contains binucleate trophoblastic cells synthesizing proteins, migrating cross the barrier and fusing with endothelial cells of the endometrium. Recently described were two glycoproteins from the family of aspartic proteases, apparently lacking the enzymatic activity: the pregnancy associated glycoproteins I and II (PAGI and PAGII). The first (PAGI) is largely secreted in maternal blood, this characteristic copes with the lack of proteolytic activity. The second (PAGII) is not completely characterized. However, it binds to lutropin (LH) receptors with high affinity. This binding allows to assume that PAGII is likely the same as the bovine chorionic gonadotropin identified earlier (bCG). A better characterization of these glycoproteins (PAGI and PAGII) and other members of the family (PAGIII...) will answer these questions together with the unexplained invasive process of the placenta.

Placental lactogen-like proteins in the rabbit placenta

Rabbit placentae and embryos at days 11 and 12 were analyzed by two-dimensional gel electrophoresis and by light microscopic histology for the presence of placental lactogen-like proteins. Immunoblotting and immunohistochemistry were performed by using a goat anti-human placental lactogen serum as well as a monoclonal mouse anti-human prolactin immunoglobulin; the results were similar. In the gel electrophoresis of placental tissue, three protein spots at pH 5.6 and 43, 39, and 35 kDa were immunostained; they were absent in the embryo. Immunoresponse was restricted to the cytotrophoblast. Immunofluorescent cells were mainly found on the proximal parts of the placental trabeculae.

Partial purification and characterization of the human placental serotonin transporter

The human placental serotonin transporter was solubilized from purified brush border membranes using digitonin as the solubilizing agent. The solubilizate was subjected to wheat germ agglutinin-Sepharose 6B column chromatography, Centricon-100 ultrafiltration and Sepharose 6B gel filtration to yield a partially purified preparation of the serotonin transporter. Specific binding of the high affinity ligand paroxetine was used to monitor the transporter during the solubilization and the purification steps. The enrichment of paroxetine binding in the final preparation was 51-fold compared to the intact brush border membranes, taking into account the inactivation that occurred during purification. The partially purified transporter exhibited paroxetine binding characteristics which were similar to those of the transporter in intact membranes. The transporter in the partially purified preparation bound paroxetine with a high affinity (dissociation constant, 0.21 nM). The binding was inhibitable by serotonin but not by other monoamines, dopamine and norepinephrine, nor by the serotonin precursor 5-hydroxytryptophan. The antidepressants, imipramine, fluoxetine and desipramine inhibited the binding with a rank order of potency of imipramine = fluoxetine > desipramine. The approximate molecular weight of the transporter was assessed by molecular sieve chromatography on Sepharose 6B and was found to be 300,000. When reconstituted into proteoliposomes, the partially purified transporter was able to catalyse NaCl-dependent serotonin transport in these proteoliposomes. The results of this study show that the human placental serotonin transporter can be solubilized, partially purified and reconstituted in a transport-competent form and, in addition, provide some insight into the protein nature of the transporter.

Demonstration of putative subunit(s) of a novel insulin receptor-associated 66 kDa GTP-binding protein, Gir

A 66 kDa GTP-binding protein, Gir, and insulin receptor (IR) were copurified from human placental membrane by DEAE-Sephacel and Wheat Germ Agglutinin (WGA)-Sepharose affinity chromatography. The WGA-fraction containing IR and Gir (IR-Gir-fraction) was phosphorylated (95 kDa IR-beta and 66 kDa Gir) by IR-tyrosine kinase using [32P]ATP or photolabeled with [32P]8-azido-GTP (mainly 66 kDa), and was cross-linked with a bifunctional reagent, bis-[sulfosuccinimidyl] suberate (BS3). The Gir cross-linked with putative subunit(s) to form a 110 kDa complex. Phosphorylation as well as 8-azido-GTP binding to Gir was not affected by cross-linking indicating that like other G-Proteins, Gir may also have subunits and that cross-linking of Gir with its putative subunits(s) does not block GTP-binding and phosphorylation sites.

Isolation, characterization and partial sequencing of Pregnancy Associated Mouse Protein PAMP1 identifies it as a novel female specific protein, unrelated to the alpha-2-macroglobulin family of proteinase inhibitors

Pregnancy Associated Mouse Protein 1 (PAMP1) was isolated from plasma of female mice. An antiserum raised against the purified protein confirmed its immunochemical identity with the originally described PAMP1. Pregnant females were observed to have plasma levels of PAMP1 that are increased two-fold at day 10-13 of gestation relative to non-pregnant females, while male mouse plasma did not contain PAMP1. The purified protein displayed an apparent subunit molecular mass of 70 kDa, irrespective of cystine reduction. The native molecular mass, estimated by gel-filtration, was about 140 kDa, indicating that PAMP1 is circulating as a non-covalent homodimer. The amino-terminal sequence of the intact protein and the internal sequences of four cyanogen bromide fragments demonstrated that this protein is not related to any known member of the alpha-2-macroglobulin family nor to any protein in the sequence databases. The physicochemical and the sequence data thus establish this protein as a novel, female-specific protein, but unrelated to the Macroglobulin proteinase inhibitor family.

Heterologous expression and characterization of prolactin-like protein-A. Identification of serum binding proteins

In this report, we describe the heterologous expression of prolactin-like protein-A (PLP-A) in Chinese hamster ovary (CHO) cells, the characterization of recombinant PLP-A, and the identification of serum PLP-A-binding proteins. CHO cell and native placental PLP-A showed similar immunoreactive characteristics and electrophoretic mobilities. N-terminal sequencing verified the identity and purity of the recombinant PLP-A species and the site of cleavage of the signal peptide from the mature secreted PLP-A species. Recombinant PLP-A lacked activity in standardized prolactin and growth hormone in vitro bioassays. Antibodies generated to recombinant PLP-A facilitated the cellular localization of PLP-A and the identification of high molecular weight PLP-A complexes. Cross-linking analyses of radioiodinated PLP-A with serum harvested from late gestation rats indicated the presence of two major cross-linked complexes migrating under reducing conditions at 130 and 250 kDa and two minor cross-linked complexes migrating at 70 and 110 kDa. Binding of PLP-A to serum proteins was specific for PLP-A and not effectively competed by other members of the prolactin/growth hormone family. The PLP-A binding species were also found in serum from non-pregnant female and male rats.

Viral validation of the manufacturing process of high purity albumin from placentas

We report on the viral validation of an industrial purification process which is used to manufacture high purity human albumin from frozen placentas. This process has been used without any modification since 1980 except for a progressive increase in production scale to reach a capacity of 19 tons of placentas per day. The extraction purification process includes five alcohol manufacturing steps, some with strict conditions of alcohol concentration, acid pH, temperature and one including chloroform. These steps are followed by three chromatographies. Albumin is finally submitted to pasteurization both in bulk and in the final container. Selected steps of this process have been tested for their ability to remove or inactivate viruses. Viruses used were HBV, HIV-1, HIV-2 and model viruses poliovirus, avian reovirus, MuLV, Sindbis, SV40 and Aujeszky's. In vitro infectivity titration assays were used for all viruses except for HBV where DNA and antigen titrations were performed. Reduction factors obtained were from 10 to 29 log10 depending on the viral marker. Moreover, testing done on regular production batches demonstrated the absence of HBV, HIV-1 and HCV genomic sequence in the final lots. Viral risk calculation for HBV, HIV-1 and HCV was made considering the maximal theoretically possible contamination of the starting material. This calculation showed the very large safety margin the manufacturing process with respect to virus transmission for these viruses or possibly other unknown ones.

alpha-Macroglobulin domain structure studied by specific limited proteolysis

Limited proteolysis was used to probe the domain structures of rat alpha 1-inhibitor 3, human pregnancy zone protein, and rat alpha 1-macroglobulin representing monomeric, dimeric, and tetrameric members, respectively, of the alpha-macroglobulin family. Specific limited digestion with trypsin, chymotrypsin, elastase, subtilisin, or Staphylococcus aureus V8 proteinase produced well-defined fragments as monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The fragments were electroblotted to polyvinylidene difluoride membranes and subjected to NH2-terminal sequence analysis to locate the cleavage sites by comparison with the known primary structures of these proteins. Based on these results and the sizes of the generated fragments the 180-kDa alpha-macroglobulin subunit is proposed to contain seven relatively large domains resistant to proteolytic digestion, constituted by approximate residues 1-200 (I), 290-400 (II), 415-660 (III), 710-860 (IVa), 920-1160 (IVb), 1203-1305 (Va), and 1314-1451 (Vb) (human alpha 2-macroglobulin numbering). The overall domain organization is similar to that recently proposed by D. S. Rubenstein, J. J. Enghild, and S. V. Pizzo (1991, J. Biol. Chem. 266, 11252-11261) from studies of rat alpha 1-inhibitor 3, but the present results suggest that the large domains IV and V proposed by these authors are each composed of two domains. The present study emphasizes that domain Vb contains the determinants necessary for receptor recognition.

Effect of guinea-pig conceptus and its secretions on endometrial prostaglandin output

The co-culture of Day-15 guinea-pig conceptuses or Day-15 pregnant guinea-pig endometrium with Day-15 non-pregnant guinea-pig endometrium had no inhibitory effect on PGF2 alpha output from the non-pregnant endometrium. Unpurified proteins secreted by the Day-15 guinea-pig conceptuses, or these proteins purified by Blue Sepharose CL-6B and ion-exchange column chromatography also had no inhibitory effect on PGF2 alpha output from Day-15 non-pregnant guinea-pig endometrium cultured in vitro. However, following the further purification of guinea-pig conceptus secreted proteins on Sephadex G-75SF, the proteins present in fraction F3:4 inhibited PGF2 alpha output from the Day-15 non-pregnant guinea-pig endometrium during the first 6 h of culture. The major protein present in F3:4 had a molecular weight of 38.2 kDa on SDS-PAGE. Proteins present in F3:4 formed only a minor proportion of the total proteins secreted. Nevertheless, the anti-luteolytic factor secreted by the guinea-pig conceptus may be this 38.2 kDa protein, but further study is required.

Biotin derivatives of endothelin: utilization for affinity purification of endothelin receptor

Three different types of biotinylated endothelin 1 (ET-1) derivatives, [Cys1]-biotinylated ET-1, [Lys9]-biotinylated ET-1, and [Cys1][Lys9]-dibiotinylated ET-1, were obtained when the biotinylation reaction was carried out with sulfosuccinimidyl-6-(biotinamido)hexanoate in an aqueous solvent. The binding of [Lys9]-biotinylated ET-1 to the ET receptor was as efficient as that of natural ET-1, whereas the binding of either [Cys1]-biotinylated ET-1 or [Cys1][Lys9]-dibiotinylated ET-1 was significantly reduced. When ET-1 was reacted with succinimidyl-6-(biotinamido)hexanoate in an organic solvent, ET-1 was exclusively modified at lysine 9. The ET receptor was then isolated from human placenta by affinity chromatography with [Lys9]-biotinylated ET-1 and avidin-agarose. The purified ET receptor was active in ET binding and was resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis into two polypeptides with apparent molecular masses of 45 and 35 kDa. The NH2-terminal amino acid sequence indicated that the two polypeptides were from an identical subtype of the ET receptor (ETB, the ligand-nonselective type). A signal peptide from Met1 to Gly26 was missing from the 45-kDa ETB, whereas 64 amino acids at the NH2 terminus were missing from the 35-kDa ETB due to proteolytic cleavage which occurred between Arg64 and Ser65. Indeed, incubation of purified ETB with endopeptidase Arg-C resulted in degradation of the 45-kDa ETB, giving rise to the 35-kDa species by a specific cleavage at Arg64. The 35-kDa ETB was active in binding to ET-1, indicating that the NH2-terminal 64-amino-acid residues are not essential for ligand binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of annexin V with prolactin in the rat anterior pituitary gland

When pituitary extracts were subjected to non denaturing polyacrylamide gel electrophoresis, an unknown protein was found to associate with a proportion of the prolactin. This protein was dissociated from prolactin by sodium dodecyl sulfate. The protein was purified and sequenced. As the amino terminus was blocked, the amino acid sequences of three peptide fragments were determined. The obtained sequences of 41 amino acids were identical to partial sequences of a known protein, rat Annexin V. The molecular mass, 36 kDa, was also the same as the molecular weight of Annexin V. The existence of Annexin V mRNA in rat pituitary glands was also confirmed by polymerase chain reaction. These results show that Annexin V, a member of the calcium-dependent phospholipid binding proteins, is synthesized in the rat pituitary gland, and suggest its association with prolatin in the gland.

Establishment of the primary structure of the major lipid-dependent Ca2+ binding proteins of chicken growth plate cartilage matrix vesicles: identity with anchorin CII (annexin V) and annexin II

Electron microscopic studies of calcifying vertebrate tissues reveal the locus of de novo mineral formation within matrix vesicles (MV). The direct involvement of MV in the initiation of mineral formation is supported by the fact that MV isolated from avian growth plate cartilage rapidly accumulate large amounts of Ca2+ and P(i) and induce mineral formation. Exploration of the constituents of MV has revealed two major protein components, a 33 and a 36 kD protein, the former of which binds to cartilage-specific collagens. These annexin-like proteins bind to acidic phospholipids in the presence of submicromolar levels of Ca2+. Antibodies raised against both the purified 33 and the 36 kD MV annexin do not cross-react with the other, indicating that they are distinct proteins. Reported here are studies elucidating the primary structure of both MV proteins using both conventional protein and molecular biologic methods. These studies establish that the 33 kD protein is nearly identical to anchorin CII (annexin V) and that the 36 kD protein is identical to avian annexin II. Immunolocalization studies show that hypertrophic chondrocytes at the calcification front of avian growth plate contain the highest level of these annexins. Further, immunogold labeling indicates that the annexins are localized within MV isolated from the growth plate. Recent studies indicate that annexin V is a new type of ion-selective Ca2+ channel protein that possesses selective collagen binding properties. Since MV are tightly associated with the collagen- and proteoglycan-rich matrix, it is tempting to speculate that this MV protein may be a component of stretch-activated ion channels that enhance Ca2+ uptake during mechanical stress.

Expression of anchorin CII, a collagen-binding protein of the annexin family, in the developing chick embryo

Expression of anchorin CII, a collagen-binding protein of the annexin family, was followed in the developing chick embryo using Northern and in situ hybridization and Western blotting. During chick somite development, anchorin CII mRNA was detected by Northern blotting as early as stage 11. At stage 24, anchorin mRNA accumulated in the anterior part of the somite sclerotome near the resegmentation line, as shown by in situ hybridization. The presence of anchorin CII protein during stages 11 to 20 was confirmed by Western blotting. In situ hybridization identified anchorin CII also in the otic vesicle adjacent to the site of contact with the statoacoustic ganglion and in the mandibular mesenchyme. The level of anchorin CII mRNA in differentiated hyaline cartilage, exemplified by sternal cartilage, was lower than that in differentiating somites or cultured chondrocytes. These findings are consistent with our notion that anchorin CII may be involved in cell-matrix interactions preceding chondrogenic differentiation events in the chick embryo. A significant level of anchorin CII mRNA and protein synthesis was also found in cultured myoblasts, but less than that in chondroblasts. This distribution pattern is different from that reported for a related protein, p34, or calpactin, the major protein substrate for tyrosine kinase phosphorylation in chick chondrocytes and fibroblasts. The results confirm suggestions from previous sequencing studies that anchorin CII and p34 are different proteins of the annexin/calpactin family.

Isolation and serine protease inhibitory activity of the 44-residue, C-terminal fragment of alpha 1-antitrypsin from human placenta

alpha 1-Antitrypsin (AAT) is a potent fluid-phase inhibitor of serine proteases. It forms a tightly bound, stoichiometric complex with these enzymes and is inactivated by cleavage within its reactive center. Evidence is here presented, that the 44-residue C-terminal fragment of AAT, termed SPAAT (short peptide from AAT), is found in human tissue, where it is apparently bound to the extracellular matrix (ECM). The identity of SPAAT was established by amino acid sequence analysis through its 40 N-terminal residues. Placental SPAAT inhibits chymotrypsin, human neutrophil elastase (HNE) and pancreatic elastase, but has no effect on trypsin. Unlike AAT, both placental and chemically-synthesized SPAAT are reversible, competitive inhibitors of chymotrypsin with Kl's of 0.92 and 7.5 microM, respectively. Both AAT and placental SPAAT also bind to diisopropyl fluorophosphate (DFP)-treated HNE as well as cathepsin G. SPAAT may therefore play an important role in the protection of ECM proteins, such as elastin, proteoglycans (PG) and/or collagen, from inappropriate attack by serine proteases.

Scatter factor is a glycoprotein but glycosylation is not required for its activity

Scatter factor (SF) is a protein produced by fibroblasts, smooth muscle cells, and human placenta which scatter cohesive epithelial cell colonies and increases cellular motility. SF bound to concanavalin A and other lectins with high affinity. SF could also be stained with a glycoprotein specific stain. Incubation of producer cells (N-ras-transformed 3T3), with tunicamycin homolog A1 did not have any significant effect on the secretory activity of SF. The treatment of SF with N- and O-glycanases as well as endoglycosidase H had no effect on its activity. However, treatment of target (Madin Darby canine kidney) cells with tunicamycin A1, abolished the scattering response. These studies suggest that scatter factor is a glycoprotein, but glycosylation is not required for its secretion or activity by the producer cells; however, glycosylation of proteins in the target cells is required for SF action.

Annexins IV (p32) and VI (p68) interact with erythrocyte membrane in a calcium-dependent manner

Purification of annexin IV and VI from porcine liver was achieved by Mono Q ion exchange chromatography at pH 8.9 and pH 7.5, respectively. The isolated proteins interacted with erythrocyte membrane as function of calcium ion and the protein concentration. Half-maximal binding of annexin VI to erythrocyte membrane was found to occur at 8 microM Ca2+. The maximal binding was estimated as 2 micrograms of annexin VI per 1 microgram or erythrocyte membrane protein, in the presence of 100 microM Ca2+. The property of erythrocyte membrane to interact with annexins was utilized in preparation of a affinity-column with polyacrylamide-immobilized erythrocyte membrane.

Proteins secreted from the early ovine conceptus block the action of prostaglandin F2 alpha on large luteal cells

In this study we evaluated whether the early conceptus secretes a factor that blocks the action of prostaglandin (PG) F2 alpha on cultured ovine large luteal cells. PGF2 alpha inhibited progesterone production by lipoprotein-stimulated large luteal cells and this anti-steroidogenic action was blocked in a dose-dependent manner by conceptus proteins secreted from Day 15 embryos. Purified ovine trophoblast protein-1 (oTP-1) did not exhibit the anti-PGF2 alpha activity, but secreted conceptus proteins devoid of oTP-1 did prevent the anti-steroidogenic effects of PGF2 alpha. This activity does not appear to be a nonspecific effect of protein since neither serum albumin nor thyroglobulin, gamma globulin, insulin, LH, secreted ovine endometrial proteins, or heat-inactivated secreted conceptus proteins had this action. After molecular-sizing chromatography we found a high- and a low-molecular weight fraction with luteal protective activity. Neither of the secreted conceptus protein fractions blocked the binding of 3H-PGF2 alpha to large luteal cells. However, conceptus proteins did block the anti-steroidogenic action of phorbol ester and calcium ionophore on large luteal cells, suggesting that secreted conceptus proteins act after activation of the free calcium/protein kinase C intracellular effector pathways. Thus, the early ovine conceptus secretes a luteal protective protein(s) that may be important for maintaining the corpus luteum during early pregnancy; however, the physiologic significance of this luteal protective protein(s) cannot be stated without further investigation.

Two forms of decidualization-associated protein and their physicochemical relationship with acute-phase alphamacrofetoprotein in rats

After isolation and purification, rat acute-phase protein, alphamacrofetoprotein and the uterine decidual protein, decidualization-associated protein were compared. They are similar in molecular weight and amino acid composition, and behave similarly during native polyacrylamide gel electrophoresis and are crossreactive with polyclonal antisera. They differ in pI values: with a mean pI of 4.83 for alphamacrofetoprotein, 5.16 for the major form of decidualization-associated protein and 4.97 for the remainder. Alphamacrofetoprotein and decidualization-associated protein differ in carbohydrate content and subunit structure, but show similar susceptibility to trypsin digestion. Evidence is provided that both the decidual species form complexes with proteases and that these are present in the extracted decidual proteins. The distribution of the forms of decidualization-associated protein in the tissues during pregnancy and parturition is described and discussed.