Identification, immunoaffinity purification and partial characterization of a human decidua-associated protein

A crude extract of pooled early-pregnancy decidual tissue was enriched for soluble decidual proteins by exhaustive affinity absorption with antibodies to human serum proteins immobilized on Eupergit C. The partly purified extract was used to prepare monoclonal antibodies. A monoclonal antibody was obtained recognizing an antigen present in extract of decidual tissue and not in extract of proliferative endometrium. The monoclonal antibody was used for immunoaffinity purification of the decidua-associated protein. By SDS-PAGE analysis, under reducing conditions it yielded 2 bands at apparent molecular weights of 55,000 and 25,000. Under non-reducing conditions a single protein band at apparent molecular weight of 200,000 was observed. The Mr 200,000 protein was named hDP200 and the Mr 55,000 protein was named hDP55. It is suggested that hDP55 is a subunit of the hDP200. The hDP200 did not react with polyclonal antibodies specific for PP12 and PP14. PP14 has been shown to be immunologically indistinguishable from PEP and alpha 2-PEG. Our data therefore suggest that hDP200 is a novel human decidua-associated protein.     

Identification, purification, and partial characterization of plasma protein kinases

Two isomeric forms of protein kinases, FI and FII, were isolated from human plasma. These two isomeric enzymes were isolated to apparent homogeneity on NaDodSO4-PAGE by using (NH4)2SO4 fractionation, DEAE-cellulose, hydroxylapatite, Affi-Gel blue, and high-pressure liquid column chromatography. Polyclonal antibodies were obtained from immunized rabbits and both enzymes cross-reacted with each other. Furthermore, immunoaffinity-purified anti-FI and anti-FII antibodies inhibited the enzyme activity of both FI and FII. These enzymes are cyclic nucleotides, Ca2+, calmodulin and phosphatidylserine-independent enzymes which can phosphorylate exogenously added histone, casein, protamine, phosvitin, and platelet surface proteins. The phosphorylated proteins of intact platelets by these enzymes in the presence of exogenously added [gamma-32P]ATP ranged in apparent molecular weights from 13.5K to 200K, as estimated by their mobility during NaDodSO4-PAGE. Trypsin removed the label from the platelet surface phosphoproteins without affecting the intracellularly located phosphoproteins labeled endogenously by 32PO4-prelabeling of intact platelets. These observations raise the possibility that these enzymes could play a role in modulating the properties of platelets through phosphorylation of the platelet surface proteins.     

Identification, purification, and partial characterization of a novel Mr 28,000 integral membrane protein from erythrocytes and renal tubules

A novel Mr 28,000 integral membrane protein ("28kDa") was identified in human erythrocytes and found entirely associated with the Triton X-100 insoluble membrane skeletons. Antibodies to 28kDa reacted strongly on immunoblots with 28kDa and a diffuse region of Mr 35,000-60,000 ("HMW-28kDa"). Selective proteolytic digestions of membranes demonstrated that HMW-28kDa has an extracellular domain, and both 28kDa and HMW-28kDa have intracellular domains. 28kDa and HMW-28kDa were purified to homogeneity. Quantitative immunoblots indicate that each erythrocyte contains 120,000-160,000 copies of 28kDa. Two-dimensional iodopeptide maps of 28kDa and HMW-28kDa were nearly identical; peptide-N-glycosidase digestion of purified HMW-28kDa demonstrated that it is the N-glycosylated form of 28kDa. When concentrated, 28kDa formed a series of larger oligomers which were stable in sodium dodecyl sulfate. Of several nonerythroid tissues studied with anti-28kDa immunoblots, only kidney displayed immunoreactive 28kDa. Purified rat kidney 28kDa was nearly identical to rat erythrocyte 28kDa when compared by two-dimensional iodopeptide mapping. Immunohistochemical staining of human kidney with anti-28kDa demonstrated prominent staining over the apical brush borders of proximal convoluted tubules. A novel integral membrane protein has been purified from erythrocyte and kidney membranes. This new protein may play a role in linkage of the membrane skeleton to the lipid bilayer.     

Identification and partial purification of a novel tumor-derived protein that induces tissue factor on cultured human endothelial cells

Conditioned medium of a human bladder carcinoma cell line (J82) was found to induce tissue factor synthesis in cultured human umbilical vein endothelial cells (HUVEC). A protein present in the J82 conditioned medium was partially purified by FPLC using a combination of MONO Q and Superose 6 columns. The bladder carcinoma-derived cytokine (BCDC) exhibited a Mr of 22 kDa by gel permeation HPLC. Polyclonal antibody against either interleukin-1, tumor necrosis factor, or transforming growth factor-beta failed to inhibit the ability of the conditioned medium to induce HUVEC tissue factor activity, suggesting that this tumor cell line secretes a novel cytokine responsible for HUVEC tissue factor induction.     

Identification and partial purification of a novel milk clotting enzyme from Onopordum turcicum

Summary Seeds, flowers and leaves of Onopordum turcicum were found to contain proteolytic enzymes able to coagulate milk. Extraction, concentration and identification of the operational parameters affecting the activity of the enzyme complex were followed by partial purification steps involving gel-filtration and ion-exchange chromatography. Milk clotting activity of the enzyme complex was tested in several steps of its purification and an increase of almost 200 fold was obtained. Molecular weight of the proteolytic enzyme fraction having the maximum activity was determined to be about 19000–24000. Isoelectric point (pI) of the enzyme complex with maximum activity was estimated to be in the range 3.3–3.7.     

Identification, purification, and characterization of a novel serine/threonine protein phosphatase from bovine brain.

A novel serine/threonine protein phosphatase is identified, and the catalytic subunit, obtained from a detergent extraction of the pellet generated by a 100,000 x g centrifugation of a whole bovine brain homogenate, is purified and characterized. The protein phosphatase, designated as PP3, has a Mr of 36,000, does not require divalent cations for activity, is stimulated rather than inhibited by inhibitor 2, is inhibited by both okadaic acid and microcystin-LR with an intermediate IC50 compared to type 1 and type 2A protein phosphatases, and preferentially dephosphorylates the beta subunit of phosphorylase kinase. Substrate specificity, immunoblotting with type-specific antisera, and the amino acid sequences of peptides derived from PP3 indicate that PP3 is not an isoform of any known serine/threonine protein phosphatase.     

Identification and purification of a protein that binds the yeast ARS consensus sequence

We have identified a yeast protein that binds specifically to the ARS consensus sequence. By two-step chromatography we have purified the factor to apparent homogeneity as a single polypeptide of 67 kd. The purified ARS consensus-binding protein (ACBP) recognizes the ARS consensus of the four genomic ARS elements tested, binding preferentially to the T-rich single strand. Point mutations in the consensus significantly reduce the affinity of the single-strand binding. At the histone H4 ARS, ACBP recognizes both the perfect ARS consensus and a 9/11 match 3' of it. These two binding sites correlate with the boundaries of the minimal functional H4 ARS element. A similar configuration of binding sites is found at ARS1. We propose a model implicating this factor in an early step of the initiation of DNA replication.     

Identification of a novel phosphatase sequence motif.

We have identified a novel, conserved phosphatase sequence motif, KXXXXXXRP-(X12-54)-PSGH-(X31-54)-SRXXXXX HXXXD, that is shared among several lipid phosphatases, the mammalian glucose-6-phosphatases, and a collection of bacterial nonspecific acid phosphatases. This sequence was also found in the vanadium-containing chloroperoxidase of Curvularia inaequalis. Several lines of evidence support this phosphatase motif identification. Crystal structure data on chloroperoxidase revealed that all three domains are in close proximity and several of the conserved residues are involved in the binding of the cofactor, vanadate, a compound structurally similar to phosphate. Structure-function analysis of the human glucose-6-phosphatase has shown that two of the conserved residues (the first domain arginine and the central domain histidine) are essential for enzyme activity. This conserved sequence motif was used to identify nine additional putative phosphatases from sequence databases, one of which has been determined to be a lipid phosphatase in yeast.     

Identification and partial purification of a large, variant form of type XII collagen.

A large, alternate form of type XII collagen has been identified in cultures of the human epidermoid cell line WISH. This form, designated XIIA, is comprised of alpha chains that are approximately 90 kDa larger than the 220-kDa alpha chain previously characterized in extracts of fetal chicken and bovine tissues. Results from both collagenase digestion and rotary shadow analysis of partially purified material show that the increase is due to a larger NC3 domain. While both the large (XIIA) and the small (XIIB) forms of type XII collagen are identified in pulse-chase radiolabeling of fetal bovine skin explant culture, they are not related in a precursor-product fashion. Inhibition studies with alpha, alpha'-dipyridyl indicate that proper folding of the collagen helix is required for complete assembly and secretion of type XIIA in WISH cell culture. The 310-kDa alpha 1A chain is likely to represent the bovine equivalent of a second translation product, estimated to be 340 kDa, predicted from analysis of one complete chick cDNA sequence. Additionally, the amino-terminal amino acid sequence of the 220-kDa bovine alpha 1B chain was determined. This sequence is very near a potential alternate splice site predicted from analysis of chicken type XII cDNA.     

Identification and purification of hydroxyisourate hydrolase, a novel ureide-metabolizing enzyme

We report the identification and purification of a novel enzyme from soybean root nodules that catalyzes the hydrolysis of 5-hydroxyisourate, which is the true product of the urate oxidase reaction. The product of this reaction is 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline, and the new enzyme is designated 5-hydroxyisourate hydrolase. The enzyme was purified from crude extracts of soybean root nodules approximately 100-fold to apparent homogeneity with a final specific activity of 10 micromol/min/mg. The enzyme exhibited a native molecular mass of approximately 68 kDa by gel filtration chromatography and migrated as a single band on SDS-polyacrylamide gel electrophoresis with a subunit molecular mass of 68 +/- 2 kDa. The purified enzyme obeyed normal Michaelis-Menten kinetics, and the K(m) for 5-hydroxyisourate was determined to be 15 microM. The amino-terminal end of the purified protein was sequenced, and the resulting sequence was not found in any available data bases, confirming the novelty of the protein. These data suggest the existence of a hitherto unrecognized enzymatic pathway for the formation of allantoin.     

Molecular identification and sequence analysis of Hillarin, a novel protein localized at the axon hillock.

The monoclonal antibody Lan3-15 identifies a novel protein, Hillarin, that is localized to the axon hillock of leech neurons. Using this antibody we have identified a full length cDNA coding for leech Hillarin and determined its sequence. The gene encodes a 1274 residue protein with a predicted molecular mass of 144013 Da. Data base searches revealed that leech Hillarin has potential orthologues in fly and nematode and that these proteins share two novel protein domains. The W180 domain is characterized by five conserved tryptophans whereas the H domains share 21 invariant residues. In contrast to the arrangement in fly and nematode the cassette containing the W180 and H domains is repeated twice in leech Hillarin. This suggests that the leech Hillarin sequence originated from a duplication event of an ancestral protein with single cassette structure.     

Porcine proparathyroid hormone. Identification, biosynthesis, and partial amino acid sequence.

Porcine parathyroid gland slices were incubated with 3H-labeled amino acids in order to label tissue proteins. After incubation a crude hormonal extract was prepared and analyzed by chromatography on carboxymethylcellulose. Among the three radioactive peaks which were detected in the eluate, two were identified as parathyroid hormone and proparathyroid hormone. Based on thin layer gel filtration in the presence of 6 M guanidine-HCl, the proparathyroid hormone had a molecular weight of 11,500 compared to about 9600 for parathyroid hormone. Radioisotope sequence analysis of the proparathyroid hormone revealed a partial sequence of: Lys1-Pro2-Ile3-Lys4-Lys5-Arg6-Ser7-Val8-Ser9--Ile11--Met14--Gly18--Ser22--Ser23---. Thus, from position 7 onward the relative position of each amino acid tested in this molecule corresponded exactly to that in the porcine parathyroid hormone sequence. The conservation of a similar, though not identical, basic hexapeptide grouping Lys-X-Y-Lys-Lys-Arg- at the amino terminal region of the prohormone in all species examined thus far (porcine, human, and bovine) suggests that this segment of the molecule may play an important role in the conversion of the prohormone to the hormone.     

Identification and partial purification of a cation-sensitive neutral endopeptidase from bovine pituitaries.

An apparently new endopeptidase with a pH optimum between 7.0 and 7.5 was purified 600 fold from bovine pituitaries. The enzyme hydrolyzed synthetic substrates such as Cbz-Gly-Gly-Leu-pNA and Cbz-Gly-Gly-Tyr-Leu-pNA by splitting the bond between the leucine residue and p-nitroaniline. Replacement of the leucine residue by alanine, greatly diminished the rate of reaction. Simple model trypsin and chymotrypsin substrates such as Bz-DL-Arg-2NA and N-succinyl-Phe-2NA were not attacked. The enzyme was also inactive toward aminopeptidase and carboxypeptidase substrates. Strong inhibition of the enzyme was observed at relatively low concentrations of sodium and potassium ions. Leupeptin, pepstatin and phenylmethylsulfonylfluoride had no effect on enzyme activity, however inhibition was obtained with p-mercuribenzoate. Preliminary experiments with filtration through Sephadex G-100 columns suggest a molecular weight in excess of 100,000.     

Identification and purification of a novel Mr 43,000 tropomyosin-binding protein from human erythrocyte membranes

A new Mr 43,000 tropomyosin-binding protein (TMBP) has been identified in erythrocyte membranes by binding of 125I-labeled Bolton-Hunter tropomyosin to nitrocellulose blots of membrane proteins separated by sodium dodecyl sulfate-gel electrophoresis. This protein is not actin, because 125I-tropomyosin does not bind to purified actin on blots. Binding of 125I-tropomyosin to this protein is specific because it is inhibited by excess unlabeled tropomyosin but not by F-actin or muscle troponins. This protein has been purified to 95% homogeneity from a 1 M Tris extract of tropomyosin-depleted erythrocyte membranes by DEAE-cellulose and hydroxylapatite chromatography, followed by gel filtration on Ultrogel AcA 44. The purified protein has a Stokes radius of 3.9 nm and a sedimentation coefficient of 2.8 S, corresponding to a native molecular weight of 43,000. Binding of 125I-tropomyosin to the purified TMBP saturates at one tropomyosin molecule (Mr 60,000) to two Mr 43,000 TMBPs, with an affinity of about 5 X 10(-7) M. The TMBP is associated with the membrane skeleton after extraction of membranes with the non-ionic detergent, Triton X-100, and is present with respect to tropomyosin at a ratio of about one for every two tropomyosin molecules. Because there is enough tropomyosin for two tropomyosin molecules to be associated with each of the short actin filaments in the membrane skeleton, the erythrocyte membrane TMBP, together with tropomyosin, could function to restrict the number of spectrin molecules attached to each of the short actin filaments and thus specify the hexagonal symmetry of the spectrin-actin lattice. Alternatively, this TMBP could be homologous to one of the muscle troponins and might function with tropomyosin to regulate erythrocyte actomyosin-ATPase activity and influence erythrocyte shape.     

Identification and partial purification of a heart mitochondrial membrane proteinase

Membrane-bound proteinase activity was demonstrated by a solid-phase assay system in both beef heart and rat liver mitochondria. The activity was sensitive to SH reagents and assorted proteinase inhibitors. Although stimulated by nonionic detergents, it became labile when solubilized by detergents. The proteinase activity from heart mitochondria copurified with the ADP:ATP translocator protein. Gel electrophoresis of this preparation revealed the translocator polypeptide as well as a number of minor components. In solubilized mitochondria the ADP:ATP translocator polypeptide slowly disappeared upon standing at 0°C as revealed by polyacrylamide gel electrophoresis under denaturing conditions. The loss of this polypeptide was prevented by addition of proteinase inhibitors as well as the translocator affinity ligand, carboxyatractylate. These observations confirm the presence of an integral membrane proteinase in mitochondria and suggest a structural and enzymatic interaction between the proteinase and the ADP:ATP translocator.Abbreviations PMSF phenylmethanesulfonyl fluoride - TPCK l-1-tosylamido-2-phenylethylchloromethyl ketone - TLCK 1-chloro-3-tosylamido-7-amino-l-2-heptanone - NEM N-ethylmaleimide - PCMBS p-chloromercuriphenylsulfonic acid - SDS sodium dodecyl sulfate - MOPS morpholinopropane sulfonate - [I₅₀] concentration of inhibitor required to give 50% inhibition     

Identification and partial purification of a protein binding to the human immunoglobulin kappa enhancer kappa E2 site.

We previously described a domain in the 5'' half of the human immunoglobulin kappa enhancer which could bind nuclear proteins in vitro, as detected by a lambda exonuclease protection assay. A second more 3'' binding domain in the enhancer has now been detected by a similar assay employing a different exonuclease, the T7 gene 6 exonuclease. Using this assay and starting with a pig spleen nuclear extract, we have purified 5000-fold a protein that binds to the 3'' domain. In a DNase I footprint experiment the partially purified protein protects a 27 bp segment in the enhancer centered around the sequence CAGGTGGC, which corresponds to the kappa E2 sequence motif described in the mouse kappa enhancer. The protein, designated NF-kappa E2, also appears to bind at a position downstream of kappa E2, at or near the kappa E3 site. Proteins capable of binding at kappa E2 are found in several mammalian species and are expressed in both lymphoid and non-lymphoid tissues.     

Immunoaffinity purification and partial amino acid sequence analysis of catechol-O-methyltransferase from pig liver

Monoclonal antibodies (mAbs) against the soluble form (S-COMT) of catechol-O-methyltransferase (COMT, EC 2.1.1.6) were produced using a purified preparation of the enzyme from pig liver as antigen. The selected monoclonal antibodies recognized the enzyme with different capacities. One of them (Co60-1B/7) showed a significant cross reaction with S-COMT from rat and human liver. A protein band of 23 kDa was recognized by the mAbs on Western blots of the soluble fraction of pig liver. The mAbs were also able to recognize the membrane-bound form of the enzyme, which was found to be mainly localized in the microsomal fraction of pig and rat liver as well as of the human hepatoma cell line Hep G2. The protein bands detected in microsomes had a molecular mass of 26 kDa in pig and rat liver and displayed a slightly higher molecular mass (29 kDa) in the Hep G2 cell line. A single step method for the immunoaffinity purification of pig liver S-COMT was developed by using a Sepharose 4B column to which the mAb Co54-5F/8 was covalently coupled. Acid elution conditions were optimized to obtain the enzyme in active form with a good yield. SDS-PAGE analysis of the purified preparation revealed a single protein band with a molecular mass of 23 kDa with 154-fold enrichment in enzyme activity over the starting material. Since the N-terminus was blocked, purified enzyme preparations were cleaved with trypsin. Two fragments of 22 and 33 amino acids in length could be sequenced by Edman degradation.     

Identification and purification of DBF-A, a double-stranded DNA-binding protein from Saccharomyces cerevisiae.

Using oligonucleotide affinity chromatography with DNase I footprinting as an assay we have looked for proteins that interact with sequence elements within the yeast origin of replication, autonomously replicating sequence 1 (ARS1). In this work we describe a protein that binds with high affinity to DNA but displays only moderate sequence specificity. It is eluted at 0.7 M salt from an ARS1 oligonucleotide column. Footprinting analysis on ARS1 at a high protein concentration revealed at least three sites of protection flanking element A and its repeats. Element A itself is rendered hypersensitive to DNase I digestion upon protein binding. This pattern is also observed for the H4 and HMR-E ARSs, suggesting that the protein alters the DNA conformation at element A and its repeats. The affinity-purified fraction is also capable of supercoiling a relaxed, covalently closed plasmid in the presence of topoisomerase. Highly purified preparations of the protein are enriched in an 18-kDa polypeptide which can be renatured from a denaturing gel and shown to bind ARS1 DNA. We have designated this protein DBF-A, DNA-binding factor A.     

Identification and partial purification of a band 3-like protein from rabbit renal brush border membranes

A monoclonal antibody against the membrane domain of human erythrocyte band 3 was tested for its ability to bind to rabbit renal brush border membranes. A single brush border protein with a molecular mass of 43 kDa was recognized by the band 3 antibody. Using DNase I coupled to an agarose-bead support this 43-kDa protein was partially purified by removing actin and a number of actin-bound proteins from the brush border membranes. The partially purified 43 kDa-band was eluted from sodium dodecyl sulfate-polyacrylamide gels and used to make a highly sensitive and specific guinea pig antiserum. This antiserum, but not serum from control guinea pigs, cross-reacts with purified band 3 from human, rabbit, and bovine erythrocytes confirming the immunologic similarity among these proteins. The 43-kDa protein can be stained by the periodic acid-Schiff base method and binds wheat germ agglutinin and concanavalin A, demonstrating that it is a glycoprotein. Furthermore, in the absence of dithiothreitol, the immunoreactive brush border protein migrates with a molecular mass of 86 kDa on an sodium dodecyl sulfate-polyacrylamide gel suggesting that under nonreducing conditions it exists as a dimer. The 43-kDa protein could be solubilized in octyl glucoside and was further purified using gel filtration chromatography. The amino acid composition of the 43-kDa brush border protein was obtained, and its similarity with erythrocyte band 3 is discussed.