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At least 613 records · Page 34Linked to original sources
PubMed1980

Identification of binding sites of turnip yellow mosaic virus protein and RNA by crosslinks induced in situ.

Turnip yellow mosaic virus RNA and protein could be crosslinked in situ by ultraviolet irradiation at pH 4.8 but not at pH 7.3, and by bisulphite treatment at pH 7.3. Crosslinked peptides could be located in the primary structure of the viral coat protein. Three regions were bound covalently by ultraviolet irradiation, and two of these three regions were bound also by bisulphite treatment. The yield of the crosslinking reaction could be high, indicating that almost all protein subunits of each virion reacted with the viral RNA. The crosslinked peptides contain most of the acidic and basic amino acids of the protein, often associated into pairs of opposite charge. Implications for the folding of the RNA into the virion and for models of RNA--protein interactions are discussed.

Cross-Linking Reagents↗
PubMed1986

Polyamines stimulate the phosphorylation of phosphatidylinositol in membranes from A431 cells.

The phosphorylation of phosphatidylinositol in plasma membranes from A431 cells was investigated using [gamma-32P]ATP as the substrate. Phosphatidylinositol 4-phosphate was found to be the major product after an incubation time of 5-10 min. Little, if any, phosphatidylinositol 4,5-bisphosphate was found under these conditions. Epidermal growth factor (EGF) had no effect on the formation of phosphatidylinositol 4-phosphate or phosphatidylinositol 4,5-bisphosphate. On the other hand, the polyamines spermidine and spermine stimulated the phosphatidylinositol kinase activity about eightfold yielding almost exclusively phosphatidylinositol 4-phosphate as the reaction product. Half-maximum stimulation by spermidine occurred under near physiological conditions (1.5 mM). Furthermore various proteins and amino acid polymers containing clustered basic amino acid residues (e.g. histones and polylysine) stimulated the formation of phosphatidylinositol 4-phosphate to a similar extent. Half-maximal concentrations for the activation were considerably lower ranging from 1.5 microM to 80 microM. The ATP specificity of the phosphatidylinositol kinase(s) was investigated with a small set of selected ATP derivatives. In the presence of spermidine the specificity changed significantly indicating that (a) spermidine acts on a kinase and not on a phosphatase, (b) this activity is distinct from the EGF-receptor protein kinase activity. The results do not suggest an involvement of the EGF receptor in the growth-factor-dependent formation of phosphatidylinositol phosphates. It is proposed that the phosphorylation of phosphatidylinositol by polyamines might be a mechanism to replenish the pool of inositolphospholipids.

1-Phosphatidylinositol 4-Kinase↗
PubMed1981

Cysteine and cystine transport at the blood-brain barrier.

The nature of cysteine and cystine uptake from the cerebral capillary lumen was studied in the rat using the carotid injection technique, [35S]-Cysteine uptake was readily inhibited by the synthetic amino acid 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH), the defining substrate for the leucine-preferring (L) system in the Ehrlich ascites cell. The addition of nonradioactive alanine or serine, representatives of the alanine, serine, and cysteine-preferring (ASC) system, produced no significant decrease in the uptake of cysteine after cysteine transport by the L system was blocked with BCH. This indicated that the major component of cysteine's transport from the brain capillary lumen was by the L system with no detectable uptake of cysteine by the ASC system. No carrier-mediated transport of cystine, the disulfide form of the amino acid, was detected, nor was there any inhibition by cystine of the transport of the neutral amino acid methionine or the basic amino acid arginine. These results suggest that the ASC system, if present, is not quantitatively important for the transport of neutral amino acids from the brain capillary lumen.

Amino Acids↗
PubMed1994

The separate and combined effect of leucine and insulin on muscle free amino acids.

The effect of insulin and leucine on amino acid and protein metabolism in muscle is not fully understood. To characterize their separate and combined effects on free amino acids in muscle and plasma, 11 volunteers received an infusion of either leucine (1 g h-1, Group 1) or glucose (20 g h-1, Group 2) for 2 h followed by a combination of the two infusions for an additional 2-h period. In muscle both the leucine infusion and the leucine plus glucose infusion increased the concentration of free leucine significantly, while the sum of the other branched chain amino acids (BCAA), of the aromatic amino acids and of the basic amino acids decreased. Glucose infusion alone decreased the sum of the essential amino acids, the BCAA and the aromatic amino acids. The combination of leucine and glucose augmented the decreases, while the concentrations of glutamate, glutamine and alanine were unaffected. In plasma the leucine infusion doubled the leucine concentration and decreased alanine, valine, methionine, tyrosine, phenylalanine and the sum of the aromatic amino acids. Glucose infusion decreased methionine, serine, isoleucine and the sum of the essential amino acids and of the BCAA. The combination of leucine infusion and hyperinsulinaemia augmented the decreases. The plasma concentrations of the keto acids of valine and isoleucine decreased by the leucine infusion while the concentrations of the keto acid of leucine and isoleucine decreased by glucose infusion. The combination of leucine and glucose had an additive effect. These effects are attributed to a specific effect of leucine on the other two BCAA and a depression of muscle proteolysis by both leucine and insulin, resulting from glucose infusion.

Adult↗
PubMed1983

Isolation and Characterization of a Xylanase from Bacillus subtilis.

Partial characterization of an extracellular xylanase isolated by chromatography from Bacillus subtilis gave a molecular weight of 32,000 and optimum pH and temperature of 5.0 and 50 degrees C, respectively. K(m) and V(max) values, determined with a soluble larchwood xylan, were 0.16% and 7.0 x 10 mumol min mg of enzyme respectively. The amino acid composition showed more basic amino acid residues than in a previously characterized xylanase from a white-rot fungus.

Journal Article↗
PubMed2003

Stress-dependent expression of a polymorphic, charged antigen in the protozoan parasite Entamoeba histolytica.

We have identified a novel stress inducible gene, Ehssp1 in Entamoeba histolytica, the causative agent of amebiasis. Ehssp1 belongs to a polymorphic, multigene family and is present on multiple chromosomes. No homologue of this gene was found in the NCBI database. Sequence alignment of the multiple copies, and genomic PCR data restricted the polymorphism to the central region of the gene. This region contains a polypurine stretch that encodes a domain rich in acidic and basic amino acids. Under normal culture conditions only one copy of this multigene family is expressed, as observed by Northern blot and RT-PCR analysis. The size of this copy of the gene is 1,077 nucleotides, encoding a protein of 359 amino acids. The polymorphic domain in this copy is 64 nucleotides long. However, on exposure of cells to stress conditions such as heat shock or oxidative stress, multiple polymorphic copies of the gene are expressed, suggesting a possible role of this gene in adaptation of cells to stress conditions. The gene copy expressed under normal conditions, and the expression profile of cells under heat stress was identical in two different strains of E. histolytica tested. Interestingly, the extent of polymorphism in this gene was very less in E. dispar, a nonpathogenic sibling species of E. histolytica. Ehssp1 was found to be antigenic in invasive amebiasis patients.

Amino Acid Sequence↗
PubMed1973

Purification and characterization of thermostable direct hemolysin of Vibrio parahaemolyticus.

A thermostable direct hemolysin was purified from culture filtrates of Vibrio parahaemolyticus. The purified hemolysin gave one precipitation line with the antihemolysin antiserum on agar-gel diffusion test and a single band on polyacrylamide gel electrophoresis. The hemolysin was not inactivated by heating at 70 to 100 C for 10 min. The hemolytic activity was not enhanced by the addition of lecithin. It was demonstrated that the hemolysin was a protein with a molecular weight of approximately 118,000. Amino acid analysis revealed that 43% of total amino acids were acidic amino acids, whereas 11% were basic amino acids.

Amino Acids↗
PubMed1981

Characterization of the predominant Azotobacter vinelandii envelope protein.

A protein with a molecular weight of 60,000 (60K) constitutes approximately 20% of the envelope protein of Azotobacter vinelandii. This protein was removed from cells and purified from other proteins by a simple washing procedure that had no effect on cell viability. Anti-60K antiserum blocked azotophage A-22 adsorption and agglutinated both vegetative cells and cysts; ferritin-conjugated antibodies used in indirect labeling studies bound uniformly to the periphery of vegetative cells. We conclude that 60K is present on the outer surface of vegetative cells and cysts. The protein is similar to the surface protein alpha of Acinetobacter ssp. in molecular weight, reassociation characteristics, and high ratio of acidic to basic amino acids. We propose that 60K forms a layer external to the outer membrane of A. vinelandii.

Agglutination Tests↗
PubMed1984

Protein on the cell surface of the moderately halophilic phototrophic bacterium Rhodospirillum salexigens.

A cell surface protein (Mr 68,000) of the moderately but obligately halophilic phototrophic bacterium Rhodospirillum salexigens was identified by two independent methods: first, by labeling the cell surface with radioactive iodine and lactoperoxidase, and second, by washing cells in 30% sucrose to remove proteins attached to the cell surface by ionic bonds. The identified protein very likely represents the outermost layer of the cell envelope of R. salexigens as observed by electron microscopy. The protein was isolated. Its isoelectric point was determined to be 4.4; the excess of acidic over basic amino acids was found to be 18.3 mol%; and its average hydrophobicity was 2.26 kJ per residue.

Cell Membrane↗
PubMed1976

Preparation and chemical properties of the outer membrane of a moderately halophilic gram-negative bacterium.

Outer membranes, almost free from peptidoglycan components, were prepared from a moderately halophilic gram-negative bacterium grown in a medium containing 2 M NaCl. The outer membrane was easily released, leaving mureinoplasts, by mild desalting in a 20% sucrose solution containing 50 mM tris(hydroxymethyl)aminomethane-HCl buffer, pH 7.8. The membrane was recovered by treatment with DNase I and CsCl buoyant density centrifugation. Chemical analyses revealed that the outer membrane was mainly composed of 31% protein, about 20% extractable lipids (mainly phospholipids), and lipopolysaccharides. The proteins had about 18 mol % excess of acidic over basic amino acids. The phospholipids comprised phosphatidyl ethanolamine, phosphatidyl glycerol, cardiolipin, and an unidentified phospholipid containing glucose, which seemed mainly associated with the outer membrane. The content of lipopolysaccharides in the outer membrane was calculated arbitrarily as 30% from the heptose content. A unique feature of these lipopolysaccharides seemed to be higher lipid content than found in lipopolysaccharides of other gram-negative bacteria. The major fatty acids of bound lipids of the outer membrane resembled those of the lipopolysaccharides obtained from cell envelope preparation and contained high concentrations of 3-hydroxy lauric acid.

Amino Acids↗
PubMed1981

Methionine transport by mycelia of Fusarium oxysporum f. sp. lycopersici.

Mycelia of Fusarium oxysporum f. sp. lycopersici accumulated L-methionine by an energy-dependent process, and the energy required for uptake may be derived from either respiration or glycolysis. The pH optimum for transport was 4 and the temperature optimum was 35 degrees C. The apparent Km for methionine uptake was 2.5-3.3 microM and the Vmax 0.24-0.30 mmol . min-1 . mg dry weight-1. S-adenosylhomocysteine (Ado-Hcys) was the major metabolic product of methionine although S-adenosylmethionine (Ado-Met), homocysteine (Hcys), and an unidentified metabolite (compound X) were also detected. The failure to demonstrate efflux of accumulated methionine in the presence of the uncoupler 2,4-dinitrophenol or excess unlabeled methionine was probably due to the fact that methionine was rapidly metabolized within the cells. Acidic and basic amino acids, and those amino acids having less than a four-carbon chain, did not inhibit methionine uptake. The rate of uptake of methionine, which was greatest in log phase mycelia, decreased substantially as the cells entered the stationary phase.

Amino Acids↗
PubMed2006

Two splice variants of claudin-10 in the kidney create paracellular pores with different ion selectivities.

Members of the large claudin family of tight junction (TJ) proteins create the differences in paracellular conductance and charge selectivity observed among different epithelia. Previous studies demonstrated that ionic charge selectivity is influenced by acidic or basic amino acids on the first extracellular domain of claudins. We noted two alternatively spliced variants of claudin-10 in the database, 10a and 10b, which are predicted to encode two different first extracellular domains and asked whether this might be a novel mechanism to generate two different permselectivities from a single gene. Using quantitative PCR, we found that claudin-10b is widely expressed among tissues including the kidney; however, claudin-10a is unique to the kidney. Using a nondiscriminating antibody, we found that claudin-10 (a plus b) is expressed in most segments of the nephron. In situ hybridization, however, showed that mRNA for 10a is concentrated in the cortex, and mRNA for 10b is more highly expressed in the medulla. Expression in Madin-Darby canine kidney (MDCK) II and LLC-PK1 cells reveals that both variants form low-resistance pores, and that claudin-10b is more selective for cations than claudin-10a. Charge-reversing mutations of cationic residues on 10a reveal positions that contribute to its anion selectivity. We conclude that alternative splicing of claudin-10 generates unique permselectivities and might contribute to the variable paracellular transport observed along the nephron.

Amino Acid Sequence↗
PubMed1982

Characterization of cysteine-containing phosphoproteins from human submandibular-sublingual saliva.

Members of a family of acidic proteins taken from human submandibular-sublingual saliva were designated cysteine-containing phosphoproteins, since they could be distinguished from other salivary phosphoproteins by the presence of half-cystine. These molecules consisted of a single peptide chain of approximately 14,000 daltons. Their isoelectric points ranged from 4.3 to 5.9. Two groups (C2 and C3) were O-phosphorylated. Their charge heterogeneity was apparently due to variations in content of phosphate and acidic and basic amino acids.

Animals↗
PubMed1976

Amino acid abnormalities in cerebrospinal fluid of patients with parkinsonism and extrapyramidal disorders.

Free amino acid determinations in the cerebrospinal fluid of patients with Parkinson's disease or other extrapyramidal disorders showed that in both groups most amino acids were increased. Significantly increased amino acids were neutral and basic amino acids. Amino acid clusters were present and corresponded with the grouping of amino acids in accordance with amino acid transport systems. The amino acids within the clusters showed a remarkable degree of correlation, and there was a notable correlation between the clusters both in the parkinsonian group and in the group of extrapyramidal disorders, but not in a control group. Our data suggest that in a number of extrapyramidal disorders, Parkinson's disease included, a more generalized abnormality exists than neuronal loss only and, in addition, that patients with these neurologic conditions have a common biochemical defect in their amino acid transport systems.

Adult↗
PubMed2004

Expression of fragments of translation initiation factor eIF4GI reveals a nuclear localisation signal within the N-terminal apoptotic cleavage fragment N-FAG.

The eukaryotic initiation factor eIF4GI plays a central role in the assembly of a competent initiation complex at the 5' end of an mRNA. Five isoforms of eIF4G exist in cells, arising from alternative translation initiation. During picornaviral infection or apoptosis, eIF4GI is cleaved proteolytically to yield distinct fragments. Using HeLa cells, we have examined the fate of these proteins in the cell. We have found that while endogenous eIF4GI is predominantly cytoplasmic, a population can also be visualised in the nucleus. Furthermore, eIF4GI is localised primarily at the nuclear periphery in the vicinity of eIF4E and PABP1. Transient transfection of HeLa cells with different myc-tagged isoforms of eIF4GI did not result in any obvious differences in their localisation. However, expression of discrete fragments of eIF4GI corresponding to those generated after apoptosis or picornaviral infection generated a distinctive, but intricate localisation pattern. Our work shows that the N-terminal apoptotic cleavage fragment N-FAG contains a sequence of basic amino acids that can act as a nuclear localisation signal. In addition, the presence or absence of the sequence flanking and including the eIF4E binding site (residues 533-682) confers a distinct cellular distribution pattern for the central domain of eIF4GI.

Amino Acid Sequence↗
PubMed1994

Genes for DNA cytosine methyltransferases and structural proteins, expressed during lytic growth by the phage phi H of the archaebacterium Halobacterium salinarium.

Lytic genes and transcription from the Halobacterium salinarium phage phi H were studied. Genes for three structural proteins were located to the left arm of the linear phage genome. The right arm was shown to encode three DNA cytosine methyltransferases, the first such sequences reported from an archaebacterium. One cytosine methyltransferase is of the N(4)-methyltransferase type. The other two open reading frames (ORFs) seem to be parts of the same gene, which has been split by a recombination event. This gene product is of the C5-methyltransferase type. The methyltransferase genes are the first phi H genes detected showing high homology to eubacterial proteins. Five of the six described gene products have a higher proportion acidic over basic amino acid residues, a common characteristic of halobacterial proteins. Lytic phi H transcription was shown to produce three RNA species, two shorter species encoding the methyltransferase genes and one large species transcribed from both the right and the left phage arm and subsequently being processed upstream of the region encoding the structural proteins.

Amino Acid Sequence↗
PubMed1996

Preparation of corn peptide from corn gluten meal and its administration effect on alcohol metabolism in stroke-prone spontaneously hypertensive rats.

Corn peptide (CP) was prepared from corn gluten meal by proteolysis with alkaline protease from alkalophilic Bacillus A-7. Free amino acids were not found in the CP product. Gel filtration on a Shodex OH-packed column revealed that the molecular weight distribution of the CP was less than about 2,000, characteristic of dipeptides to decapeptides, i.e. oligopeptides. The amino acid pattern of CP was similar to that of corn gluten meal, which was rich in alanine and branched-chain amino acids, but poor in basic amino acids. The effect of the CP administration on alcohol metabolism was examined with SHR-SP, which were given ethanol orally through a gastric tube at the rate of 1.0 g/kg. Prior administration of CP at 1.0 g/kg resulted in fast disappearance of ethanol and its oxidative product acetaldehyde from the blood relative to the control without administration. Hence, it is suggested that CP, rather than its constituent amino acids such as alanine and proline, effectively takes part in enhancing the metabolism of ethanol as well as acetaldehyde.

Acetaldehyde↗