Protein requirement of the prawn Marsupenaeus japonicus estimated by a factorial method

The protein requirement to give maximum body protein retention in the prawn Marsupenaeus japonicus was assessed by determining both daily protein needed for maintenance (M) and daily body protein increment (G) when the juvenile prawn was maintained on a diet containing high quality protein. The body protein increment was obtained by determining carcass nitrogen increment when the prawn was fed on casein-based diets. The protein required for maintenance was estimated by regressing weight gains of the prawn on the diets containing graded levels of casein. True daily increase or retention of body protein in the prawn corresponded to the sum of G and M, and it was 3.2 g protein per kg body weight per day. The dietary protein requirement of juvenile M. japonicus for maximum body protein retention was suggested to be about 10 g per kg body weight per day providing that the prawn was fed the casein-based diet containing 50% crude protein (net protein utilization = 32) at the feeding level of 2%.     

Recombinant Human Ribosomal Protein S16: Expression,Purification, Refolding,and Structural Stability

The cDNA of human ribosomal protein S16 was cloned into the expression vector pET-15b. Large-scale production of the recombinant protein was carried out in E. coli cells and highly purified protein was isolated. A method for refolding the protein from inclusion bodies was optimized. The secondary structure content of the refolded protein was analyzed by CD spectroscopy. It was found that 21 +/- 4% of the amino acid sequence of the protein forms alpha-helices and 24 +/- 3% is in beta-strands. The protein structure stability was studied at various pH values and urea concentrations. The protein is quickly denatured at pH above 8.0, whereas increasing of urea concentration causes slow unfolding of the protein.     

Hyperproduction of a bifunctional hybrid protein, metapyrocatechase-protein A, by gene fusion.

A hybrid protein between metapyrocatechase and Staphylococcal protein A was produced by recombinant DNA techniques. A plasmid carrying the fusion gene that encodes the hybrid protein was constructed and expressed in E. coli. Over 70% of soluble proteins of the cell extracts was estimated to be the hybrid protein. This fusion protein is about 65,000. Both the IgG-binding activity of protein A and the metapyrocatechase activity were found in the hybrid protein. The optimum pH of metapyrocatechase in the fusion protein was at around 6.5 and Km was 1.3 X 10(-5) M. A simple immuno-enzymometric assay was developed for anti-BSA antibody using the fusion protein.     

Severe acute respiratory syndrome coronavirus 7a accessory protein is a viral structural protein

Severe acute respiratory syndrome coronavirus (SCoV) 7a protein is one of the viral accessory proteins. In expressing cells, 7a protein exhibits a variety of biological activities, including induction of apoptosis, activation of the mitogen-activated protein kinase signaling pathway, inhibition of host protein translation, and suppression of cell growth progression. Analysis of SCoV particles that were purified by either sucrose gradient equilibrium centrifugation or a virus capture assay, in which intact SCoV particles were specifically immunoprecipitated by anti-S protein monoclonal antibody, demonstrated that 7a protein was associated with purified SCoV particles. Coexpression of 7a protein with SCoV S, M, N, and E proteins resulted in production of virus-like particles (VLPs) carrying 7a protein, while 7a protein was not released from cells expressing 7a protein alone. Although interaction between 7a protein and another SCoV accessory protein, 3a, has been reported, 3a protein was dispensable for assembly of 7a protein into VLPs. S protein was not required for the 7a protein incorporation into VLPs, and yet 7a protein interacted with S protein in coexpressing cells. These data established that, in addition to 3a protein, 7a protein was a SCoV accessory protein identified as a SCoV structural protein.     

Binding of anticoagulant vitamin K-dependent protein S to platelet-derived microparticles.

Vitamin K-dependent protein S is an anticoagulant plasma protein serving as cofactor to activated protein C in degradation of coagulation factors Va and VIIIa on membrane surfaces. In addition, it forms a noncovalent complex with complement regulatory protein C4b-binding protein (C4BP), a reaction which inhibits its anticoagulant function. Both forms of protein S have affinity for negatively charged phospholipids, and the purpose of the present study was to elucidate whether they bind to the surface of activated platelets or to platelet-derived microparticles. Binding of protein S to human platelets stimulated with various agonists was examined with FITC-labeled monoclonal antibodies and fluorescence-gated flow cytometry. Protein S was found to bind to membrane microparticles which formed during platelet activation but not to the remnant activated platelets. Binding to microparticles was saturable and maximum binding was seen at approximately 0.4 microM protein S. It was calcium-dependent and reversed after the addition of EDTA. Inhibition experiments with monoclonal antibodies suggested the gamma-carboxyglutamic acid containing module of protein S to be involved in the binding reaction. An intact thrombin-sensitive region of protein S was not required for binding. The protein S-C4BP complex did not bind to microparticles or activated platelets even though it bound to negatively charged phospholipid vesicles. Intact protein S supported binding of both protein C and activated protein C to microparticles. Protein S-dependent binding of protein C/activated protein C was blocked by those monoclonal antibodies against protein S that inhibited its cofactor function. In conclusion, we have found that free protein S binds to platelet-derived microparticles and stimulates binding of protein C/activated protein C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development of a protein microarray using sequence-specific DNA binding domain on DNA chip surface

A protein microarray based on DNA microarray platform was developed to identify protein-protein interactions in vitro. The conventional DNA chip surface by 156-bp PCR product was prepared for a substrate of protein microarray. High-affinity sequence-specific DNA binding domain, GAL4 DNA binding domain, was introduced to the protein microarray as fusion partner of a target model protein, enhanced green fluorescent protein. The target protein was oriented immobilized directly on the DNA chip surface. Finally, monoclonal antibody of the target protein was used to identify the immobilized protein on the surface. This study shows that the conventional DNA chip can be used to make a protein microarray directly, and this novel protein microarray can be applicable as a tool for identifying protein-protein interactions.     

Identification of a new protein involved in the regulation of the anticoagulant activity of activated protein C. Protein S-binding protein

The apparent molecular weight of functional protein S in citrated plasma was observed to be between 115,000 and 130,000 as measured by sedimentation equilibrium in the air-driven ultracentrifuge. The molecular weight of the functional protein decreased to approximately 62,000 when copper ions were added to the plasma. This suggested the presence of a protein S-binding protein in plasma, which was confirmed by gel filtration experiments. Frontal analysis of plasma indicated that functional protein S could exist in as many as three forms. Addition of copper ions to plasma reduced the number of forms to one. In order to isolate the binding protein, plasma was fractionated first on a column of immobilized iminodiacetic acid that had been equilibrated with copper ions. The proteins that eluted in a 0.6 M NaCl wash were passed over a column of protein S immobilized on agarose beads. A protein, eluted in the 0.6 M NaCl wash, was observed to bind to protein S in gel filtration experiments. When added to plasma depleted of both protein S and the binding protein, the binding protein was observed to enhance the anticoagulant activity of activated protein C only in the presence of protein S. Protein S-binding protein was also observed to enhance the rate of factor Va inactivation by activated protein C and protein S.     

Formation of Protein Bodies in the Starchy Endosperm of Rice (Oryza sativa L.): A Re-investigation

The mechanism of protein body formation in the starchy endospermis described for two rice varieties, one of normal protein contentand the other high in protein. Three types of protein bodieswere found in both rices. While each protein body type was depositeddifferently, the mechanism of formation for the same type inthe two varieties was analogous. First secreted was the largespherical protein body. It was deposited within rough endoplasmicreticulum, had a dense centre and a concentric ring appearance,and was bounded by a single membrane. The second protein bodyto form was crystalline, was found in vacuoles, and was secretedvia the Golgi apparatus. The third type, the small sphericalprotein body, was secreted late in development, was depositedin vesicular rough endoplasmic reticulum, and lacked dense centresand concentric rings. The high protein rice had a thicker sub-aleuronelayer than the normal protein rice. Oryza sativa L., rice, protein bodies, starchy endosperm, ultrastructure     

Isolation and Characterization of a Novel Chitosan-Binding Protein from Non-Heading Chinese Cabbage Leaves

To know the mechanism of ammonia assimilation in non-heading Chinese cabbage (Brassica campestris L. ssp. chinensis (L.) Makino) leaves regulated by chitosan (CTS), a CTS-binding protein was isolated from non-heading Chinese cabbage leaves using the chitosan affinity chromatography approach and this CTS-binding protein was partially characterized. The profile of the 53.1 kDa purified protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was compared with the native molecular weight of 106.5 kDa, which indicated that the purified protein was a dimer with identical subunits. After isoelectric focusing, a band was obtained at pH 8.25. The agglutination test and periodic acid-Schiff staining further revealed that the protein was a glycoprotein with lectin activity. Moreover, the purified protein contained 17.4% (w/w) neutral carbohydrate and 82.56% (w/w) protein. The comparison of this protein and the 67 kDa CTS-binding protein isolated previously from Rubus culture tissue exhibited some differences in characterization. According to results of peptide mass fingerprinting analysis, the protein purified in the present study does not show any similarity with any protein in the protein data bank. Thus, it was deduced that the protein purified in the present study is a novel CTS-binding protein.     

Transepithelial transport of a viral membrane glycoprotein implanted into the apical plasma membrane of Madin-Darby canine kidney cells. II. Immunological quantitation

The envelope of vesicular stomatitis virus was fused with the apical plasma membrane of Madin-Darby canine kidney cells by low pH treatment. The fate of the implanted G protein was then followed using a protein A- binding assay, which was designed to quantitate the amount of G protein in the apical and the basolateral membranes. The implanted G protein was rapidly internalized at 31 degrees C, whereas at 10 degrees C no uptake was observed. Already after 15 min at 31 degrees C, a fraction of the G protein could be detected at the basolateral membrane. After 60 min 25-48% of the G protein was basolateral as measured by the protein A-binding assay. At the same time, 25-33% of the implanted G protein was detected at the apical membrane. Internalization of G protein was not affected by 20 mM ammonium chloride or by 10 microM monensin. However, the endocytosed G protein accumulated in intracellular vacuoles and redistribution back to the plasma membrane was inhibited. We conclude that the implanted G protein was rapidly internalized from the apical surface of Madin-Darby canine kidney cells and a major fraction was routed to the basolateral domain.     

Cytotoxicity of pokeweed antiviral protein

Pokeweed antiviral protein, a plant protein which inactivates eukaryotic ribosomes, was found to be cytotoxic to both HeLa and Vero cells. Cellular protein synthesis was inhibited by exposure of the cells to microM concentrations of the antiviral protein for 24 h periods or longer. The extent of the inhibition of cellular protein synthesis was dependent upon the time of exposure to pokeweed antiviral protein and was partially reversed by washing the cells at various times prior to the measurement of protein synthesis. The antiviral protein was also observed to bind nonspecifically to cells at both 4 degrees and 34 degrees C. The data indicate that the pokeweed antiviral protein is capable of slowly entering mammalian cells which results in the inhibition cellular protein synthesis.     

Cross-linking of the proteins in the outer membrane of Escherichia coli.

1. The organization of the proteins in the outer membrane of Escherichia coli was examined by the use of cross-linking agents and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Treatment of protein A-peptidoglycan complexes with dithiobis(succinimidyl propionate) or glutaraldehyde produced the dimer, trimer, and higher oligomers of protein A. Both forms of this protein, proteins A1 and A2, produced similar cross-linking products. No cross-linking of protein A to the peptidoglycan was detected. 2. The proteins of the isolated outer membrane varied in their ease of cross-linking. The heat-modifiable protein, protein B, was readily cross-linked to give high molecular weight oligomers, while protein A formed mainly the dimer and trimer under the same conditions. The pronase resistant fragment, protein Bp, derived from protein B was not readily cross-linked. No linkage of protein A to protein B was detected. 3. Cross-linking of cell wall preparations, consisting of the outer membrane and peptidoglycan, showed that protein B and the free form of the lipoprotein, protein F, could be linked to the peptidoglycan. A dimer of protein F, and protein F linked to protein B, were detected. 4. These results suggest that specific protein-protein interactions occur in the outer membrane.     

The cytoplasmic tail of the human respiratory syncytial virus F protein plays critical roles in cellular localization of the F protein and infectious progeny production

The importance of the F protein cytoplasmic tail (CT) for replication of human respiratory syncytial virus (HRSV) was examined by monitoring the behavior of viruses expressing F proteins with a modified COOH terminus. The F protein mutant viruses were recovered and amplified under conditions where F protein function was complemented by expression of a heterologous viral envelope protein. The effect of the F protein modifications was then examined in the context of a viral infection in standard cell types (Vero and HEp-2). The F protein modifications consisted of a deletion of the predicted CT or a replacement of the CT with the CT of the vesicular stomatitis virus (VSV) G protein. In addition, engineered HRSVs that lacked all homologous glycoprotein genes (SH, G, and F) and expressed instead either the authentic VSV G protein or a VSV G containing the HRSV F protein CT were examined. We found that deletion or replacement of the F protein CT seriously impaired the production of infectious progeny. Cells infected with viruses bearing CT modifications displayed increased F protein surface expression and increased syncytium formation. The distribution of F protein in the plasma membrane of infected cells was altered, resulting in an F protein that was evenly distributed rather than localized predominantly to virus-induced surface filaments. CT deletion or exchange also abrogated interaction of F protein with Triton-insoluble lipid rafts. Addition of the F protein CT to the VSV G protein, expressed as the only viral glycoprotein in an HRSV genome, had the opposite effects: the number of infectious progeny was higher, the surface distribution was changed from relatively even to localized, and the proportion of VSV G protein associated with lipid rafts was higher. Together, these results show that the HRSV F protein CT plays a critical role in F protein cellular localization and production of infectious virus and suggest that the function provided by the CT is independent of the F protein ectodomain and transmembrane domain and is mediated by F protein-lipid raft interaction.     

The 38 kDa Ca2+/membrane-binding protein of pig granulocytes needs a high Ca2+ concentration to be phosphorylated by protein kinase C

The 38 kDa Ca2+/membrane-binding protein reported to be the dominant substrate of protein kinase C in the extracts of pig neutrophil granulocytes was purified partially and its phosphorylation was investigated. In pig granulocytes type II protein kinase C was the major isoform, while type III isoenzyme was present only as a minor activity. Phosphorylation of the 38 kDa protein was performed with rat brain protein kinase C. Each of the three isoenzymes purified from rat brain was able to phosphorylate this protein, though on the conditions used in our experiments it was phosphorylated most intensively by type II protein kinase C. A phospholipid-dependent, but Ca2(+)-independent, form of protein kinase C was demonstrated with the aid of a synthetic oligopeptide substrate. Phosphorylation of the 38 kDa protein by the Ca2(+)-independent enzyme proceeded exclusively in the presence of Ca2+. The Ca2+ concentration necessary for the phosphorylation of the 38 kDa by either form of protein kinase C was by orders of magnitude higher than that required for the activation of protein kinase C.     

Newly Imported Rieske Iron-Sulfur Protein Associates with Both Cpn60 and Hsp70 in the Chloroplast Stroma

The precursor of the Rieske FeS protein, a thylakoid membrane protein, was imported by isolated pea chloroplasts, and the mature protein was shown to be integrated into the cytochrome bf complex of the thylakoid membranes. Insertion into the thylakoid membrane was sensitive to the ionophores nigericin and valinomycin, suggesting a requirement for a proton motive force. A considerable proportion of the imported Rieske protein was detected in the stromal fraction of the chloroplasts, and this increased when membrane insertion was blocked with ionophores. Electrophoresis of the stromal fraction under nondenaturing conditions resolved two distinct complexes containing the Rieske protein. One of these complexes was identified as an association of the Rieske protein with the chaperonin Cpn60 complex by its electrophoretic mobility, Mg-ATP-dependent dissociation, and immunoprecipitation with anti-Cpn60 antibodies. Coimmunoprecipitation of imported Rieske protein with anti-heat shock protein 70 (Hsp70) antibodies indicated that the Rieske protein was also associated, in an ATP-dissociable form, with a chloroplast Hsp70 homolog. Immunoprecipitation analysis of an import time course detected the highest amounts of the Cpn60-Rieske protein complex early in the time course, whereas highest amounts of the Hsp70-Rieske protein complex were formed much later. The disappearance of the Cpn60-Rieske protein complex correlated with increased amounts of the Rieske protein in the thylakoid fraction.     

Isolation of characterization of a major outer membrane protein of Pseudomonas aeruginosa. Evidence for the occurrence of a lipoprotein.

In the outer membrane of P. aeruginosa, a protein of apparent molecular weight 8,000 (protein I) is present as a major protein. Purification and chemical analysis of protein I were carried out. This protein was purified by essentially the same procedure as for the purification of the E. coli lipoprotein, which was developed by Inouye et al. (J. Bacteriol. (1976) 127, 555--563). The amino acid composition of protein I was determined. Protein I lacks proline, valine, isoleucine, phenylalanine, tryptophan, and half-cystine. Fatty acid analysis of the protein revealed that it contained 0.89 mol of fatty acids per mol of protein. Among the fatty acids hexadecanoic acid (C16:0) was predominant. In an in vivo labeling experiment, [2-3H]glycerol was incorporated into protein I. A protein with similar mobility to protein I on urea-SDS polyacrylamide gel electrophoresis was isolated from the purified peptidoglycan of P. aeruginosa by trypsin digestion. The amino acid composition of this protein was essentially the same as that of protein I. These results indicate that the outer membrane of P. aeruginosa contains a protein analogous to the E. coli lipoprotein, although considerable differences were observed in the amino acid composition and the fatty acid content.     

Phosphorylation of liver gap junction protein by protein kinase C

The 27 kDa protein, a major component of rat liver gap junctions, was shown to be phosphorylated in vitro by protein kinase C. The stoichiometry of the phosphorylation indicated that approx. 0.33 mol phosphate was incorporated per mol 27 kDa protein. Phosphorylation was entirely dependent on the presence of calcium and was virtually specific for serine residues. For comparison, the gap junction protein was also examined for its phosphorylation by cAMP-dependent protein kinase, the extent of phosphorylation being one-tenth that exerted by protein kinase C.     

Isolation and Characterization of a Novel Chitosan-Binding Protein from Non-Heading Chinese Cabbage Leaves

To know the mechanism of ammonia assimilation in non-heading Chinese cabbage (Brassica campestris L. ssp. chinensis (L.) Makino) leaves regulated by chitosan (CTS), a CTS-binding protein was isolated from non-heading Chinese cabbage leaves using the chitosan affinity chromatography approach and this CTS-binding protein was partially characterized. The profile of the 53.1 kDa purified protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis was compared with the native molecular weight of 106.5 kDa, which indicated that the purified protein was a dimer with identical subunits. After isoelectric focusing, a band was obtained at pH 8.25. The agglutination test and periodic acid-Schiff staining further revealed that the protein was a glycoprotein with lectin activity. Moreover, the purified protein contained 17.4 % (w/w) neutral carbohydrate and 82.56% (w/w) protein. The comparison of this protein and the 67 kDa CTS-binding protein isolated previously from Rubus culture tissue exhibited some differences in characterization. According to results of peptide mass fingerprinting analysis, the protein purified in the present study does not show any similarity with any protein in the protein data bank. Thus, it was deduced that the protein purified in the present study is a novel CTS-binding protein.     

胃癌患者Sox2蛋白和CTHRC-1蛋白的表达与肿瘤发展密切相关

本研究选取病理科收集的自2016年1月至2016年12月的90例术后胃癌组织标本(胃癌组)、45例癌旁组织标本(对照组),采用免疫组化染色法检测两组标本中的Y框蛋白(Sox2)、胶原三股螺旋重叠蛋白-1表达,并分析其与肿瘤TNM分期、淋巴结转移、浸润深度、分化程度的关系,采用Spearman秩相关检验检测两种蛋白的相互关系,试图探讨胃癌患者癌组织中性别决定区Y框蛋白(Sox2)、胶原三股螺旋重叠蛋白-1(CTHRC-1)的表达及其相关性。研究结果表明:胃癌组的Sox2蛋白阳性表达率63.33%显著低于对照组的93.33%(p<0.05),胃癌组的CTHRC-1蛋白阳性表达率78.89%显著高于对照组的24.44%(p<0.05);胃癌组的Sox2蛋白阳性表达与胃癌的分化程度、发生淋巴结转移具有相关性(p<0.05);胃癌组的CTHRC-1蛋白阳性表达与胃癌的淋巴结转移、TNM分期、肿瘤浸润深度具有显著的相关性(p<0.05);胃癌组的Sox2蛋白与CTHRC-1蛋白呈显著的负相关表达(Spearman相关系数r=-0.322, p=0.002<0.05)。本研究的初步结论表明:胃癌组织中Sox2蛋白低表达和CTHRC-1蛋白高表达,并且与肿瘤发展密切相关,且二者表达呈负相关。     

Determination of nonspecific lipid transfer protein in rat tissues and Morris hepatomas by enzyme immunoassay

Rat tissues contain a nonspecific transfer protein which in vitro mediates the transfer of diacylphospholipids as well as cholesterol between membranes. This protein appears identical to sterol carrier protein. A specific enzyme immunoassay for this protein was developed using antibodies raised in rabbits, against a homogeneous protein from rat liver. This assay was based on the very high affinity of the nonspecific lipid transfer protein for polyvinyl surfaces. A reproducible adsorption was achieved by presenting the protein to the surface in the presence of a large excess of bovine serum albumin. The adsorbed protein was detected with specific immunoglobulin (IgG) isolated by antigen-linked affinity chromatography and a goat anti-rabbit IgG-enzyme conjugate. Adsorption was proportional to the amount of protein present, giving rise to a linear standard curve. The enzyme immunoassay measured transfer protein levels in the range 0.2-2 ng. The highest concentrations of transfer protein were found in liver and intestinal mucosa. Levels in other tissues including brain, lung, kidney, spleen, heart, adrenals, ovary and testis were 5-10-fold lower than in liver. In the fast-growing Morris hepatoma 7777 the concentration of nonspecific lipid transfer protein was approximately one-tenth of that measured in the host liver, whereas a reduction of 65% was observed in the slow-growing Morris hepatomas 7787 and 9633. Subcellular distribution studies showed that approx. 70% of the transfer protein was present in the soluble supernatant fraction.