Affinity modification of 80S ribosomes from human placenta by derivatives of tri- and hexauridylates as mRNA analogs]

Derivatives of 5'-32P]labeled (pU)3 and (pU)6 bearing 4-(N-2-chloroethyl-N-methylamino)benzylmethylamine residues attached to 5'-phosphates via phosphamide bond were applied to the affinity labeling of 80S ribosomes from human placenta. The reagents had normal coding properties and were fixed in the ribosomal mRNA-binding region by codon-anticodon interaction with cognate Phe-tRNA(Rhe) at P site (in the case of (pU)3 derivative) or at both A and P sites (in the case of (pU)6 one). Both reagents were found to modify only the 40S subunit. The sites of the reagents attachment to 18S ribosomal RNA were identified by blot-hybridization of the modified 18S rRNA with restriction fragments of the corresponding rDNA. They were found to be located within positions 976-1057 for (pU)6 derivative and within 976-1164 for (pU)3 one. These sites are located presumably within highly conserved parts of the eukaryotic small subunit rRNA secondary structure.     

Affinity modification of human chromatin with reactive derivatives of oligonucleotides.

Reaction of 4-(N-2-chloroethyl-N-methylamino)benzylphosphamides of oligonucleotides (RCl-(pT)16 and RCl-(pApC)6) with human chromatin in intact nuclei and with metaphase chromosomes has been investigated. The oligonucleotides were targeted to poly(A) and poly(TG)-repeating DNA sequences. It was found that the reagents alkylate DNA and some proteins due to specific complex formation. The affinity character of the reaction was proved by the fact that free corresponding oligonucleotides taken in excess or preliminary treatment of chromatin with S1-nuclease both prevent the biopolymers from modification. The results obtained evidence that in human chromatin there are open DNA sequences available for affinity modification with oligonucleotide derivatives. Analysis of patterns of modified proteins within these chromatin areas may give a key to the structure of these chromatin sites.     

S-Adenosylhomocysteine hydrolase from human placenta. Affinity purification and characterization.

S-Adenosylhomocysteine hydrolase (EC 3.3.1.1) was purified to homogeneity from human placenta by using S-adenosylhomocysteine-agarose affinity chromatography. The enzyme is a tetramer with a native Mr of 189 000 and subunit Mr of 47 000-48 000; there were nine cysteine residues per subunit and no disulphide bonds. The pI was 5.7. H.p.l.c. analysis revealed that the enzyme contained four molecules of tightly bound cofactor (NAD) per tetramer, of which 10-50% was in the reduced form. The enzyme had four binding sites per tetramer for adenosine, of which 10-35% were found to be occupied. Two types of adenosine-binding sites could be distinguished on the basis of differences in rates of dissociation of the enzyme-adenosine complex, and by examining binding of adenosine at 0 degree C and 37 degrees C. The enzyme catalysed the interconversion of adenosine and 4',5'-dehydroadenosine; the equilibrium constant for this reaction was 2.1 and favoured 4',5'-dehydroadenosine formation. Variability in the specific activity of preparations of S-adenosylhomocysteine hydrolase was related to the NAD+/NADH ratio of the preparation. The capacity to bind radioactively labelled adenosine depended on the adenosine content of the purified enzyme. The rate of adenosine binding and the sensitivity of S-adenosylhomocysteine hydrolase to inactivation by adenosine were both diminished in the absence of dithiothreitol.     

Preparation of iduronate sulfatase from the human placenta]

The preparation of the enzyme iduronate sulfatase from human placenta has been undertaken. The substrate O-(alpha-L-idopyranosyluronic acid 2-sulfate) (1 leads to 4)-2,5-anhydro-D-[3H]mannitol 6-sulfate was used to measure the enzymatic activity. The enzyme shows a pH optimum of 4.0 in 0.1 M sodium formiate or acetate buffer. Chromatography on DE-52 gives a 5.4 fold purification. The enzyme is inhibited by NaCl or KCl: in 20 mM salt the reaction rate was only 63% and 34% respectively. Inhibition by salt can be removed by extensive dialysis after the chromatographic step.     

Affinity modification of creatine kinase from rabbit skeletal muscle by 2',3'-dialdehyde derivatives of ADP and ATP

Periodate-oxidized ADP and ATP (oADP and oATP) are substrates and affinity reagents for creatine kinase from rabbit skeletal muscle. oADP and oATP modified a lysine epsilon-amino group in the nucleotide-binding site of the enzyme. Complete inactivation is observed upon binding 2 moles oADP per 1 mole of the enzyme dimer. Modification with oADP is described by a liner dependence of the log of enzyme activity on time, testifying to a pseudo-first-order of the reaction. The reaction rate constant (ki = 8.10(3) min-1) and dissociation constant for the reversible enzyme-oADP complex (Kd = 62 microM) were determined. ADP protected the enzyme from inactivation and covalent binding of the analog, whereas oADP covalently bound to the enzyme was phosphorylated by phosphocreatine. The data obtained allow to suggest that the epsilon-amino group of a lysine residue of the active site is located in close proximity to ribose of ATP and ADP forming a complex with the enzyme. This group seems essential for correct orientation of the nucleotide polyphosphate chain in the enzyme active center, but take no immediate part in the transphosphorylation process.     

Genesis of islands in the human placenta]

A fetal origin of the isalnds was supposed after light microscopical observations, investigated especially on young placentas. Electron microscopical examination confirm this supposition. The following facts prove, that the islands are products of the trophoblast: 1. The development of Langhans-cells to the differentiated cytotrophoblast, passing the state of the transitional cell type - I have called the differentiated cytotrophoblast "trophocyte". 2. The linkage of the trophocyte to the syncytiotrophoblast of the islands by desmosomes. 3. Definite morphological differences between the trophocytes and the decidual cells. 4. The absence of connective tissue and vessels in the islands.     

Isolation and properties of glycerol-3-phosphate oxidoreductase from human placenta

Glycerol-3-phosphate oxidoreductase (sn-glycerol 3-phosphate: NAD+ 2-oxidoreductase, EC 1.1.1.8) from human placenta has been purified by chromatography on 2,4,6-trinitrobenzenehexamethylenediamine-Sepharose, DEAE-Sephadex A-50 and 5'-AMP-Sepharose 4B approximately 15800-fold with an overall yield of about 19%. The final purified material displayed a specific activity of about 88 mumol NADH min-1 mg protein-1 and a single protein band on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The native molecular mass, determined by Ultrogel AcA 44 filtration, was 62000 +/- 2000 whereas the subunit molecular mass, established on polyacrylamide gel in the presence of 0.1% sodium dodecyl sulphate, was 38000 +/- 500. The isoelectric point of the enzyme protein, determined by column isoelectric focusing, was found to be 5.29 +/- 0.09. The pH optimum of the placental enzyme was in the range 7.4-8.1 for dihydroxyacetone phosphate reduction and 8.7-9.2 for sn-glycerol 3-phosphate oxidation. The apparent Michaelis constants (Km) for dihydroxyacetone phosphate, NADH, sn-glycerol 3-phosphate and NAD+ were 26 microM, 5 microM, 143 microM and 36 microM respectively. The activity ratio of cytoplasmic glycerol-3-phosphate oxidoreductase to mitochondrial glycerol-3-phosphate dehydrogenase in human placental tissue was 1:2. The consumption of oxygen by human placental mitochondria incubated with the purified glycerol-3-phosphate oxidoreductase, NADH and dihydroxyacetone phosphate was similar to that observed in the presence of sn-glycerol 3-phosphate. The possible physiological role of glycerol-3-phosphate oxidoreductase in placental metabolism is discussed.     

Affinity labeling of arginyl residues at the catalytic region of estradiol 17 beta-dehydrogenase from human placenta by 16-oxoestrone

16-Oxoestrone inhibited competitively the activity of estradiol 17 beta-dehydrogenase from human placenta against estradiol in phosphate buffer (pH 7.2), suggesting reversible binding of 16-oxoestrone to the substrate-binding site. 16-Oxoestrone irreversible inactivated the estradiol 17 beta-dehydrogenase in borate buffer (pH 8.5) in a time-dependent manner, following pseudo-first-order kinetics. The rate constant (k3) obtained for the inactivation by 16-oxoestrone was 8.3 x 10(-4) s-1. The rate of inactivation was significantly decreased by addition of estrone, estradiol, estriol, NAD(H) and NADP+. Also, the rate was reduced markedly by 2'AMP, 5'ATP and 2',5' ADP, but not by NMN(H) and 3-pyridinealdehyde adeninediphospho nucleotide. The inactivation by 16-oxoestrone was neither prevented by sodium azide nor influenced by light. From these data, 16-oxoestrone, an alpha-dicarbonyl steroid, was suggested to inactive estradiol 17 beta-dehydrogenase by modification of arginyl residues located around the substrate-binding site of the enzyme. Biphasic inactivation of the enzyme by 16-oxoestrone was observed with an increase of modified arginyl residues. The first phase of the inactivation was regarded as an affinity labeling of the arginyl residues at or near the substrate-binding site of the enzyme. Stoichiometry of the inactivation indicated that two arginyl residues were essential for maintenance of the enzyme activity. The second phase was considered as chemical modification of the arginyl residues outside of the catalytic region of the enzyme.     

Alkylation of estradiol 17beta-dehydrogenase from human placenta with 3-chloroacetylpyridine--adenine dinucleotide.

3-Chloroacetylpyridine--adenine dinucleotide, which is active as a hydride acceptor (Km = 0.6 mM), inactivates and alkylates estradiol 17beta-dehydrogenase. The kinetics of inactivation by 3-chloroacetylpyridine--adenine dinucleotide and the absence of inactivation by 3-chloroacetylpyridine ribose phosphate show that the alkylation follows the formation of a binary complex (Kd = 4.5 X 10(-4) M). Studies of the labelling by 3-chloro[2-14C]acetylpyridine--adenine dinucleotide and the rate of alkylation as a function of pH, give evidence to the alkylation of a cysteine, the stoichiometry being one mole per subunit. The 14C label is distributed between three chymotryptic peptides, one of which accounts for about 50% of the radioactive label.     

Affinity modification of Escherichia coli ribosomes with 2',3'-O-[4-(N-2-chloroethyl)-N-methylamino]-benzylidene derivative of AUGU3 in the 70S initiation complexes

Affinity labelling of the Escherichia coli ribosomes with the 2',3'-O-[4-(N-(2-chloroethyl)-N-methylamino]benzylidene derivative of AUGU3(AUGU3[14C]CHRCl) has been studied within 70S initiation complexes ribosome.AUGU3[14C]CHRCl.fMet-tRNA(Metf) and binary complex ribosome.AUGU3[14C]CHRCl. Various ways of the 70S initiation complex formation resulted in differently labelled products. Proteins S5, S7, S9, L1, L16 were thus identified as cross-linked with AUGU3[14C]CHRCl within an initiation complex obtained in the presence of initiation factors IF-1, IF-2, IF-3, whereas only proteins S5 and S7 were cross-linked within the complex obtained with the sole factor IF-2. Proteins S1, S3, L1 and L33 were labelled within the initiation complex obtained nonenzymatically but only protein S1 within the binary complex. In all complexes formed with use of initiation factors labelling of IF-2 factor was invariably observed.     

Affinity alkylation of E. coli RNA-dependent DNA polymerase with TTP gamma-amidate derivatives]

TTP gamma-benzylamidates are shown to act as competitive inhibitors of poly(dT) synthesis catalyzed by E. coli RNA-dependent DNA polymerase. The KM value for TTP as well as KI values for the gamma-analogues have been determined. TTP gamma-4-(N-2-chloroethyl-N-methyl-amino)benzylamidate is shown to be an effective affinity reagent for this enzyme.     

Affinity modification of E. coli RNA-polymerase in a complex with the promoter by phosphorylating derivatives of primer oligonucleotides

Oligonucleotides 2 to 7 nucleotide residues long, complementary to the codogenic strand of T7 promoter A2, have been synthesized; all of them contained a ribo-unit at the 3'-end. They were converted into 5'-(N-methyl)phosphoimidazolides, and the affinity reagents obtained were allowed to bind covalently to RNA polymerase in the presence of a promoter. Some of the nucleotide residues covalently attached occupied proper positions relative to the active centre of the phosphodiester bond synthesis and on addition of [alpha-32P]UTP were elongated, so that highly selective affinity labelling occurred. With oligonucleotides of various lengths, different distribution of the label between beta, beta' and sigma subunits of RNA polymerase took place. Most efficient was labelling of beta-subunit by the residue--pCpGpCpU, and of sigma-subunit by the residue--pApApApTp-CpGpCpU (p--radioactive phosphorus atom). In both cases, the amino acid residues labelled were histidines.     

Affinity modification of DNA-dependent RNA-polymerase from phage T7 with 5'-p-fluorosulfonylbenzoyl adenosine: the effect of modification on the interaction with substrates

T7 RNA polymerase, covalently modified with 5'-p-fluorosulfonylbenzoyl adenosine, looses the ability of binding the promoter (pGEM-2 plasmid) and poly(dC) template as well as the initiating nucleoside triphosphate (GTP). However the enzyme retains the unspecific binding with DNA fragments of considerable length.     

15-Hydroxyprostaglandin dehydrogenase from human placenta. 1. Isolation and characterization]

15-Hydroxyprostaglandin dehydrogenase was isolated from human term placenta up to a final purification of 380-fold. A spec. act. of 2000 mU/mg of protein was reached. The preparation was not homogeneous as judged by analytical disc electrophoresis. The enzyme could be stored in the presence of 50% glycerol and 10mM 2-mercaptoethanol without any loss of activity for at least one year. A distinct single protein band stained after discontinuous polyacrylamide gel electrophoresis was shown by enzymatic activity staining to correspond to 15-hydroxyprostaglandin dehydrogenase activity. Thus no evidence for the exitstence of isoenzymes was obtained. The protein in the final preparation steps showed neither alcohol dehydrogenase, NAD reductase, nor NADH oxidase activity, nor enzymatic conversion of prostaglandin or 15-oxoprostaglandin in the absence of NAD and NADH. No spontaneous reactions between NAD and prostaglandin or NADH and 15-oxoprostaglandin were detectable in the absence of the enzyme. Ethanol and glycerol slightly inhibited the reaction. Various buffers (Tris/HC1, potassium phosphate, HEPES, and triethanolamine) and salts (ammonium chloride, ammonium sulfate, potassium chloride, and sodium chloride) had different effects on the reaction rate. The pH profile of the reaction shows a plateau between pH 7.0 and 7.8 and a steep maximum at pH 9.5. A linear Arrhenius plot was obtained for the temperature dependence of the reaction from 20 to 37 degrees C. The molar activation enthalpy of the reaction was calculated to be 13.1 kcal/mole. The molecular weight of 15-hydroxyprostaglandin dehydrogenase was estimated to be 32000 -/+ 3000 by gel filtration on Sephadex G-150 in the presence of 10mM mercaptoethanol.     

A method of isolation and properties of DNA-dependent DNA-polymerase epsilon from human placenta]

DNA polymerase epsilon was purified to near homogeneity from human placenta. The enzyme has one subunit (170 kDa, sedimentation coefficient 8.2S), intrinsic 3'-5'-exonuclease activity, it is independent on PCNA and high processivity on poly(dA)-oligo(dT) template-primer without PCNA. It was shown, that the enzyme incorporates 3'-amino-2',3'-dideoxythymidine 5'-triphosphate in DNA, after that synthesis is stopped. Simultaneously DNA polymerase alpha was purified.