Studies on endogenous phosphorylation of chicken erythrocyte membranes. Calcium-dependent phosphorylation of specific proteins

In this work, endogenous phosphorylation of chicken erythrocyte membranes was investigated. The membrane proteins were rapidly phosphorylated endogenously (half maximum time was 30 s) in the presence of millimolar concentration of Mg2+ under physiological conditions. As an exogenous substrate, protamine was phosphorylated most rapidly of those tested, and histone, casein and bovine serum albumin were rather poor substrates. Cyclic nucleotides had no effect on the endogenous membrane phosphorylation. EGTA inhibited the phosphorylation of a membrane protein having an approximate molecular weight of 43000, and this inhibition was reversed by the addition of a stoichiometric amount of Ca2+. Furthermore, trifluoperazine, an inhibitor of calmodulin, was found to have the same effect as that of EGTA. The phosphorylated 43 kDa protein could be extracted from the membranes under high salt conditions, and was precipitated specifically with anti-actin antibody. These results suggest that the phosphorylation of a peripheral membrane protein (which has an approximate molecular weight of 43000) of chicken erythrocytes by membranous protein kinase(s) depends on Ca2+ and possibly on calmodulin.

Effect of morphinone on opiate receptor binding and morphine-elicited analgesia

Specific binding of 3H-naloxone to opiate receptors was found to be irreversibly inactivated by morphine. This inactivation exhibited pseudo-first-order kinetics. The presence of sulfhydryl compounds or morphine during incubation with morphinone proved good protection. Morphinone-pretreated mice blocked the analgesic effect of morphine. The possible mechanism for these observations is proposed as follows: morphinone binds covalently to sulfhydryl group of opiate receptors, and inactivates irreversibly opiate binding sites, thus blocking the analgesic effect of morphine.

Different cytotoxicity of ricin and a concanavalin A-ricin A chain conjugate between Balb/3T3 cells and the transformed cells

In the previous paper, we reported that ricin and a concanavalin A-ricin A chain conjugate were more toxic to normal cell lines than the transformed variants. In this work, we confirmed this conclusion using other cell lines (KB 3 flat, ST-balb and R4-IudR) which were derived from the Balb/3T3 clone. KN7-8 had a lower number of Con A binding sites than the sensitive parent line (A-31), while the apparent association constant of Con A and surface receptors KN7-8 was slightly higher than that of A-31. On the other hand, both cell lines had almost the same number of ricin binding sites, while the apparent association constant of KN7-8 was lower than that of A-31. These differences in the number of binding sites and the apparent association constant might not be due to the different sensitivity of these cell lines to the toxin, because the amounts of bound 125I-ricin internalized into the two cell lines during incubation at 37 degrees C were essentially the same. Furthermore, no evidence was obtained showing that there was a difference between A-31 and KN7-8 cells in the ability of reduction of the disulfide bond of ricin, degradation of internalized toxin and in the sensitivity of the protein synthesizing machinery.

Purification and some properties of a cyclic AMP-binding protein from human erythrocyte membranes

A cyclic AMP-binding protein of human erythrocyte membranes was solubilized with 0.3% Triton X-100 in 10 mM Tris-HCl (pH 7.4) at 4 degrees C, and purified by DEAE-cellulose column chromatography and affinity chromatography on a cyclic AMP derivative-fixed Sepharose 4B column. The purified cyclic AMP-binding protein showed a single band (molecular weight: 49,000) on examination by sodium dodecyl sulfate polyacrylamide gel electrophoresis and the band was specifically labeled with a photoaffinity analogue of cyclic AMP, 8-N3-cyclic [2-3H]AMP. This protein bound 1.6 mol of cyclic AMP per molecule with an association constant of 3.8 x 10(9) M-1 and the optimum pH for binding was 7.4. The protein inhibited the activity of a purified protein kinase from human erythrocyte membranes [Suzuki, K., Terao, T., & Osawa, T. (1981) J. Biochem. 89, 1--11], while cyclic AMP restored the enzymic activity. The amino acid composition of this protein was different from those of cytoplasmic cyclic AMP-binding proteins. These observations indicate that the cyclic AMP-binding protein purified in this work is the regulatory subunit of a membrane bound cyclic AMP-dependent protein kinase.

Effect of local anesthetics on the inhibition of protein synthesis by ricin

In the previous paper, 1) we indicated that local anesthetics such as dibucaine and procaine reduced the toxic action of ricin on Balb/3T3 clone A-31 cells, while these drugs did not show such an effect on KN7-8, a transformed variant of clone A-31. To clarify the different action of the local anesthetics on the cytotoxicity of ricin toward the normal and the transformed cells, some of the possibilities were examined. Dibucaine did not show any influence on the rate of uptake of 125I-ricin into the cells. Furthermore, the rate of reduction of the disulfide bond between the A and B chains, and degradation of ricin in the cells were unaffected by dibucaine. However, the inhibition of the poly U-directed protein synthesizing system from A-31 cells by ricin was reduced in the presence of a low concentration of dibucaine or procaine. Therefore, the most probable explanation for the reduced sensitivity to the toxin in normal cells in the presence of the local anesthetics is that these drugs have some influence on the protein synthesizing system of the normal cells and reduce the inhibitory action of the toxin.

Protective effect of sulfhydryl compounds on acute toxicity of morphinone

The ability of sulfhydryl compounds to provide protection against the acute toxicity of morphinone was investigated in mice. Subcutaneous administration of morphinone produced a reduction of hepatic non-protein sulfhydryl concentration. Pretreatments of mice with glutathione or cysteine significantly increased the survival rate of mice given a lethal dose of morphinone, whereas morphinone lethality was markedly potentiated by diethyl maleate. On the other hand, the administration of morphine produce a dose dependent reduction of hepatic non-protein sulfhydryl contents. However, neither glutathione nor cysteine protected mice from the acute toxicity of morphine. A possible explanation for these observations was proposed as follows: morphine is oxidized by morphine 6-dehydrogenase to morphinone, and the morphinone thus produced decreases the sulfhydryl contents in the liver. This mechanism is supported by the fact that morphinone reacts easily with glutathione and cysteine in vitro.

Support effects on iron(III) oxide catalyst in the reduction of nitrogen oxide with hydrogen

Catalytic reduction of NO with H2 has been carried out over Fe2O3 dispersed on ten kinds of supports. Among the carrier oxides, Fe2O3 on SiO2 was the most effective catalyst and Fe2O3 on SnO2 was least active. The surface states and adsorption states of NO on supported Fe2O2 were studied by means of i.r. and M�ssbauer spectroscopies. The intensities of the i.r. bands at 1810 and 1735 cm-1 of the adsorbed NO on reduced iron sites are discussed in connection with the catalytic activity.

Purification and characterization of a catalytic subunit of an adenosine 3':5'-monophosphate-dependent protein kinase from human erythrocyte membranes

Protein kinase [EC 2.7.1.37] of human erythrocyte membranes was solubilized with 0.5 M NaCl in 5 mM phosphate buffer, pH 6.7 at 4 degrees C and purified on a CM-Sephadex C-50 column, followed by affinity chromatography on a histone-Sepharose 4B column. The purified protein kinase gave a single band (molecular weight; 41,000) on examination by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimum pH of the enzyme was 8.0 and a millimolar range of concentration of Mg2+ was required for its maximum activity. Histone and protamine were well phosphorylated by the protein kinase but casein and phosvitin were poor phosphate acceptors for the enzyme. The enzymic activity was not stimulated by cyclic AMP (cAMP). A cAMP-finding protein from human erythrocyte membranes inhibited the activity of the protein kinase, but the activity was restored with cAMP. A heat stable protein inhibitor from rabbit skeletal muscle also inhibited this enzyme. From these observations, this protein kinase seemed to be a catalytic subunit of the membrane bound cAMP-dependent protein kinase. This enzyme was strongly inhibited with Ca2+ in the presence of 1 mM MgCl2. Various sulfhydryl reagents and polyamines also had inhibitory activity on the protein kinase. Natural substrates of the enzyme were investigated using heat treated membranes and 0.5 M NaCl extracted membrane residues. Band 4.1, 4.2, and 4.5 proteins were phosphorylated but band 2 (spectrin) and band 3 proteins were poor substrates for this protein kinase.

Preparation of antibody (IgG)-ricin A-chain conjugate and its biologic activity

As a model experiment for the preparation of cancer chemotherapeutic agents, a disulfide-linked conjugate of rabbit anti-mouse IgG (RaMIgG) and ricin A-cahin was synthesized. Activated sulfhydryl groups were first introduced into RaMIgG and then the modified RaMIgG was reacted with ricin A-chain. The fraction containing the conjugate was obtained from the reaction mixture by gel filtration through Sephadex G-150 and was characterized by sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis and double immunodiffusion in agar. The inhibitory activity of A-chain against protein synthesis in a cell-free system and the binding activity of RaMIgG to mouse B lymphocytes were both fully retained. The purified conjugate selectively inhibited protein synthesis in mouse B lymphocytes possessing cell surface Ig, but not that in thymocytes. The cytotoxicity was inhibited by adding mouse IgG and an excess amount of RaMIgG to the cell culture. The effects of unlinked RaMIgG and A-chain on the cytotoxicity were negligible even when the two were used as a mixture.

Studies on adenosine 3',5'-monophosphate phosphodiesterase of human erythrocyte membranes

In this work we show the existence of cyclic AMP phosphodiesterase (EC 3.1.4.17) in human erythrocyte membranes and have clarified some properties of the enzyme. In human erythrocytes, about 23% of the total cyclic AMP phosphodiesterase activity is in a membrane-bound form. Although it could be solubilized with Triton X-100 in 5 mM Tris-HCl buffer (pH 8.0), it was not solubilized by a low or high concentration of salt. The enzyme seems to be localized in the cytoplasmic surface, since it is detected in sealed inside-out vesicles of human erythrocyte membranes, but not in intact human erythrocytes. The optimum pH was found to lie between 7.4 and 8.0, and Mg2+ was found to be necessary for its activity. Ca2+ and calmodulin could not stimulate the activity of this enzyme. Theophylline was a strong inhibitor, but cyclic GMP could not inhibit the enzymic hydrolysis of cyclic [32P]AMP and this membrane-bound enzyme therefore seems to be specific to cyclic AMP.

Alpha-casein-binding proteins of guinea pig macrophage membranes and their possible roles in chemotaxis

The existence of specific binding proteins for alpha-casein, a well-known potent chemoattractant, on guinea pig peritoneal macrophages was demonstrated. Binding of 3H-alpha-casein to macrophages was found to be specific and reversible. Its association constant and the number of binding sites were 5.0 X 10(-6) M and 7.5 X 10(5) per cell, respectively. The presence of formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe), another chemoattractant, at a chemotactically active concentration (10(-11) to 10(-6) M) reduced this binding significantly. Pretreatment of macrophages with proteases such as trypsin and chymotrypsin decreased the number of binding sites for alpha-casein and the chemotactic response to alpha-casein. alpha-Casein binding proteins were isolated from radiolabeled macrophage surface membranes by affinity chromatography on a column of alpha-casein Sepharose 4B. SDS-polyacrylamide gel electrophoresis of the isolated proteins revealed three radioactive bands; two (MW 130,000 and 65,000) were glycoproteins, and the other (MW 100,000) was a protein which contained little carbohydrate. These three proteins were also isolated from the same source by affinity chromatography using a column of fMet-Leu-Phe-AH-Sepharose. This result, together with the observation that fMet-Leu-Phe inhibited the binding of alpha-casein to macrophages, indicated that alpha-casein and the tripeptide have at least partly common binding sites on guinea pig macrophages. Some of the proteins obtained in this work may constitute chemotactic receptors on the macrophage membrane.

[Studies on the shift of cefmetazole into the gastrointestinal tract (author's transl)]

From the studies on the stability of cefmetazole and cefazolin in feces of animals and children, and the determination of the fecal concentration of cefmetazole in three pediatric patients, the following results were obtained. 1) When cefmetazole was kept at 37 degrees C for 24 approximately 48 hours in feces of rats, rabbits, dogs and children, it showed no decrease of the potency. On the other hand, cefazolin kept in the same condition as that of cefmetazole showed a remarkable decrease of the potency. 2) Fecal excretions of cefmetazole were 0, 0.22 and 0.65% of total doses, respectively, in two pediatric patients of scarlet fever and one pediatric patient of serous meningitis.

Preparation of concanavalin A-ricin A-chain conjugate and its biologic activity against various cultured cells

For the development of therapeutic agents that possess tissue-specific carriers, a method was devised to synthesize an artificial protein hybrid conjugate containing a moiety which binds to a cell membrane receptor and an active fragment of a toxic protein. By the introduction of an activated sulfhydryl group into concanavalin A (Con A), a conjugate of Con A and the ricin A-chain cross-linked with a disulfide linkage was synthesized. The purified conjugate was studied with regard to its inhibitory activity against protein synthesis in cell-free and cultured cell systems. The Con A-rich A-chain conjugate retained about one-third the inhibitory activity of ricin in a cell-free protein synthesis system. It also was highly toxic to cultured normal cells. These results indicate that the conjugate is a structural and functional analog of ricin and that the original membrane-binding chain (B-chain of ricin) could be replaced by Con A. Transformed cells were insensitive to this conjugate and required a longer preincubation time. The sensitivity of the normal cells was reduced in the presence of local anesthetics.

Covalently cross-linked monovalent, divalent, and tetravalent derivatives of concanavalin A

Dimeric succinyl-concanavalin A was cross-linked with ethylenediamine using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide a condensing agent. Thus, a divalent dimer and a tetravalent tetramer composed mostly of covalently cross-linked subunits bearing altered net charges were obtained. Photoaffinity labeling of the cross-linked dimer with p-azidophenyl alpha-D-mannopyranoside resulted in a specific label for its saccharide-binding site and yielded a nonvalent dimer and a monovalent dimer (showing no subunit exchange). However, hemagglutination and glycogen precipitation data suggested that the labeled binding site is shielded but not destroyed by the label and can still bind weakly an external saccharide ligand possibly due to unsteadiness of the shielding label. Although nonvalent and monovalent derivatives were mitogenic as well as divalent and tetravalent derivatives for mouse splenic lymphocytes, binding and stimulation experiments indicated that their stimulating efficiencies after binding to the cells were far lower than those of the multivalent counterparts. Their activities were inhibited by methyl alpha-D-mannopyranoside, suggesting that the weak activities of nonvalent and monovalent derivatives were due to the labeled sites entirely and partly, respectively. We suggest that the triggering of lymphocyte mitogenesis by concanavalin A may depend on cross-linkage of cell surface receptors.

Binding of bacterial lipopolysaccharide to histocompatibility-2-complex proteins of mouse lymphocytes

The membrane binding sites for lipopolysaccharide (LPS) were isolated by affinity chromatography of the solubilized membranes prepared from 125I-labeled mouse B-cells and T-cells on an affinity adsorbent prepared by coupling Salmonella minnesota R595 LPS to activated Sepharose 4B. The membrane proteins bound to the affinity adsorbent and eluted with 1.0% Triton X-100 were analyzed according to their mobility on polyacrylamide gel electrophoresis in sodium dodecylsulphate. These membrane proteins were further identified by immunoprecipitation with specific antisera. Immunoglobulins, possibly immunoglobulins M and D, were identified in the eluate from the B-cell membranes. The histocompatibility-2-complex proteins (H-2D, H-2K and Ia antigens) were also found to be binding sites for LPS on both B-cells and T-cells.

The effect of metal complex of thyrotropin-releasing hormone on locomotor activity of neonatal chicken

Neonatal chickens were injected intraventricularly with Ni(II), Pd(II), Cu(II) or Zn(II) complex of TRH and the potencies of stimulating locomotor activity were compared with that of TRH, Ni(II)-TRH was more potent than the ligand while Pd(II)-TRH was inert. Cu(II)- and Zn(II)-TRH induced the response to the same extent of the ligand. These results indicate that the action of TRH in the CNS resulting in the locomotor hyperactivity is dependent on the tertiary conformation of molecule which is modified by chelate formation.