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M A Nesmeianova

Publications and source records attributed to M A Nesmeianova.

At least 19 recordsLinked to original sources
PubMed1996

[Disruption of processing of alkaline phosphatase as a result of single amino acid changes affects the composition and metabolism of phospholipids from Escherichia coli, secreting mutant proteins].

Amino acid substitutions in the cleavage site of the E. coli alkaline phosphatase signal peptide Val for Ala(-1) or Pro for Arg(+1) result in the block of the enzyme processing. In cells secreting such mutant proteins the relative content and rate of turnover of anionic phospholipids (phosphatidylglycerol and cardiolipin) are increased. The rise of the transfer of the phosphoglycerol residue from phosphatidylglycerol to periplasmic membrane derived oligosaccharides or to the model substrate, arbutin performed by the activity of phosphoglycerol transferase I testifies to phosphatidylglycerol accumulation on the outer surface of the cytoplasmic membrane. The results suggest of phosphatidylglycerol interaction with the alkaline phosphatase precursor and their subsequent joint translocation through the cytoplasmic membrane of E. coli.

Alkaline Phosphatase↗
PubMed1996

[Isolation and certain properties of mutant alkaline phosphatase of Escherichia coli].

Natural and mutant alkaline phosphatases with amino acid substitutions in the processing site and N-terminal domain of the mature polypeptide chain Val for Ala(-1), Gln for Glu (+4) and simultaneously Gln for Glu (+4) and Ala for Arg (+1) have been isolated from the periplasm and cultural fluid of E. coli. It has been found that these substitutions have little effect on the dependence of the enzyme activity on pH, ionic strength and temperature but influence its isoenzymic spectrum and decrease (almost twofold) the maximal rate of the enzyme-catalyzed reaction. Extracellular enzymes display, in contrast with periplasmic ones, other catalytic properties (Vmax) and binding activity (Km). After translocation through the outer membrane all the enzymes display decreased Vmax and increased Km. These changes are especially well-pronounced in case of the mutant protein PhoA46 which contains an uncleaved signal peptide due to the impossibility of processing resulting from the substitution of Val for Ala(-1). The Vmax for this protein is decreased 20 times, while the Km is increased 4-fold. The protein also shows a higher (in comparison with other proteins) sensitivity towards proteolytic enzymes and is less resistant upon storage. The experimental data suggest that the changes in the N-end of alkaline phosphatase located at a long distance from its active center influence the enzyme function.

Alkaline Phosphatase↗
PubMed1996

[Analysis of the effect of replacing Lys(-20) in the alkaline phosphatase signal peptide on secretion of this enzyme].

The effect of substitutions for the positively charged Lys(-20) in the N-terminal domain of the E. coli alkaline phosphatase signal peptide on enzyme secretion has been studied. Mutant alkaline phosphatases were obtained by the amber-suppressor method. An amber mutation was introduced in the appropriate position of the alkaline phosphatase gene using oligonucleotide-directed mutagenesis. This was followed by mutant protein synthesis in E. coli strains producing amber-suppressor tRNAs specific for Tyr, Gly, Ala, Glu, Phe, His, Cys, and Pro. All the mutant proteins can by translocated through the cytoplasmic membrane and form in the periplasm a molecule possessing an enzymatic activity. However, some amino acid substitutions decrease the rate of protein maturation their effect depends not only on the charge of the amino acid residue but also on its nature. Thus, introduction of positively charged. His and the polar uncharged Tyr is without effect, while negatively charged Glu and hydrophobic Ala, Phe and Pro residues as well as Gly and Cys have an inhibiting action. The results obtained testify to the importance of the signal peptide terminal domain primary structure in secretion.

Alkaline Phosphatase↗
PubMed1996

[Changes in indicators of the antioxidant defense system in patients with ischemic heart disease treated conventionally].

Parameters of antioxidant defense including superoxide dismutase, catalase and spontaneous chemiluminescence were studied in 68 patients with ischemic heart disease and 20 control patients. The above parameters decreased with the disease aggravation. Conventional therapy has improved antioxidant defense, the effect being dependent on effect of therapy irrespective of its variant.

Adrenergic beta-Antagonists↗
PubMed1995

[Permeability of the Escherichia coli outer membrane for ethidium ions and periplasmic alkaline phosphatase during increased synthesis of it].

During augmented synthesis of periplasmic alkaline phosphatase by various strains of Escherichia coli, the outer membrane of bacterial cells becomes permeable for both the enzyme and ethidium ions which do not generally penetrate inside the cells of gram-negative bacteria. In the absence of the lipoprotein in the outer membrane, its permeability for these compounds as well as its sensitivity to membranotropic agents increases, thus testifying to the influence of the lipoprotein upon certain properties of the outer membrane. A competitive interaction was found between the lipoprotein and lipopolysaccharide content in the outer membrane and their content and alkaline phosphatase secretion into the external medium. It is suggested that increased permeability of the E. coli outer membrane during augmented synthesis of the secreted protein is due to impaired biogenesis of membrane components.

Alkaline Phosphatase↗
PubMed1995

[Changes in biogenesis and secretion of periplasmic alkaline phosphatase, coded by the phoA gene included in the Escherichia coli DH1 plasmid].

Augmented synthesis of periplasmic alkaline phosphatase from E. coli DH1 coded by the phoA gene within the composition of plasmid pHI-7 results in alterations in the enzyme biogenesis, such as accumulation of intermediate enzyme forms corresponding to various stages of its posttranslational modification, and alternative localization. The cell cytoplasm was found to contain a large proportion of alkaline phosphatase precursors in the form of insoluble aggregates. The mature enzyme was detected in both the periplasm and the cultural fluid in the form three methazymes with an increased (as compared with the original strain) content of methazymes I and II. The cell envelope of E. coli DHI transformed by plasmid pHI-7 with the phoA gene differed from that of the original strain by an increased acid phospholipid (cardiolipin/phosphatidylglycerol) ratio as well as by increased distribution density of intramembrane particles on the surface of the cytoplasmic membrane facing the cytoplasm. Changes in the biogenesis of the enzyme during its augmented synthesis are due to disturbances in the equilibrium between the synthesis of polypeptide chains, on the one hand, and their translocation and processing, on the other, apparently as a result of restricted secretion sites and lack of inhibition of translation of secreted proteins in bacteria.

Alkaline Phosphatase↗
PubMed1988

[Effect of the protonophore carbonylcyanide-m-chlorophenylhydrazone on the localization of secreted alkaline phosphatase in E. coli].

It was shown that the total amount of synthesized alkaline phosphatase as well as the value of enzymatic activity in E. coli cells decrease in the presence of the protonophore, carbonylcyanide-m-chlorophenylhydrazone. The enzyme content in the periplasm also decreases, while the amount of the enzyme bound to the spheroplasts increases. This effect is enhanced with a rise in the protonophore concentration. An electron cytochemical analysis showed that in the presence of the protonophore, alkaline phosphatase is partly localized in the cytoplasm and on the inner surface of the cytoplasmic membrane, which is unobserved in control cells. It was assumed that carbonylcyanide-m-chlorophenylhydrazone suppresses the translocation of alkaline phosphatase across the cytoplasmic membrane and enzyme biosynthesis, on the whole.

Alkaline Phosphatase↗
PubMed1982

[Interaction of alkaline phosphatase and acid phospholipids in E. coli cells and artificial membranes].

The synthesis of alkaline phosphatase, an enzyme secreted by E. coli, is decreased in the cells pretreated with the lipotropic antibiotic polymixin prior to derepression. The decrease of the enzyme synthesis in the cell is correlated with the changes in the intracellular and intramembrane ratios of acid phospholipids, presumably at the level of the cytoplasmic membrane. The interaction between alkaline phosphatase and artificial lipid membranes has been shown to be a function of pH and ionic strength and is increased in the liposomes rich in acid phospholipids and decreased in the polymixin-treated liposomes.

Alkaline Phosphatase↗
PubMed1981

[Influence of alcohol lipotropic agents on biosynthesis and repression of secreted alkaline phosphatase in Escherichia coli].

Preincubation of cells in the presence of 4% ethanol accompanied by an increase of non-saturated cis-vaccenic acid content was shown to promote synthesis of alkaline phosphatase. Preincubation of cells in 0.1% hexanol reducing the level of this acid, on the contrary, leads to partial repression of the enzyme synthesis; the lag-phase of repression in the cells with a raised content of non-saturated cis-vaccenic acid and, consequently, with a greater fluidity of lipids was also shown to be reduced. Conversely, the reduction of lipid membrane fluidity on ethanol addition simultaneously with the repressing metabolite ortho-phosphate extends the lag-phase of repression and removes it partially during cell cultivation in the presence of ortho-phosphate. The impact of lipid composition variations on the synthesis and repression of alkaline phosphatase is discussed.

Alcohols↗
PubMed1981

[Comparative study of properties of periplasmic and membrane-bound alkaline phosphatase of E. coli].

The properties of three forms of periplasmic and one form of membrane-bound alkaline phosphatase of E. coli were studied. A practically complete agreement between the conditions for optimal activity of these enzymes (pHopt 9.5 +/- 0.1), effect of ionic strength and temperature, and accordance between the substrate specificities (the enzymes decompose all types of phosphate-containing ether bonds) were observed. A similarity was shown between the kinetic parameters (Km = 3.9 x 10(-5) + 4.3 x 10(-5) M) for the reaction of p-nitrophenylphosphate decomposition), type and constants of inhibition (Ki) of these enzymes by phosphate-containing compounds as well as between the values of energy (E = 5.95 + 6.2 kcal/mole) for activation of decomposition of this substrate. A structural similarity of active sites of these enzymes was assumed. It was also suggested that the membrane-bound form of the enzyme is a precursor of the periplasmic one.

Alkaline Phosphatase↗
PubMed1979

[Exogenous orthophosphate regulation of ATPase activity of E. coli cells].

The effect of exogenous orthophosphate and mutations in genes, regulating the Pi transport system, on the ATPase activity of E. coli subcellular fractions was studied. It was shown that the orthophosphate starvation resulted in the cessation of the increase in the ATPase activity of membranes and was accompanied by the increase in the analogous activity of a soluble fraction at the expense of the derepression of alkaline phosphatase possessing this activity. The disturbance, resulted from the mutation of protein components participating in the specific binding and transport of orthophosphate, changed the ATPase activity of subcellular fractions: increased the ATPase activity of soluble fraction (independently of the presence of orthophosphate in medium), did not affect significantly the activity of membrane--bound ATPase in the presence of orthophosphate and decreased this activity in the absence of orthophosphate. The data obtained point to the fact that components, binding exogenous orthophosphate and transporting it into a cell, affect the rigidity of the ATPase bound E. coli cytoplasmic membrane. Mutations resulting in the defect in these components relax this bound and lead to the detection of ATPase proper in the periplasm.

Adenosine Triphosphatases↗
PubMed1979

[Interrelationship between metabolic and genetic regulation of alkaline phosphatase and poly- and pyrophosphatases].

The effects of orthophosphate and mutations in the regulatory genes of alkaline phosphatase on the activities of pyrophosphatase and polyphosphatase of E. coli were studied. It was shown that orthophosphate represses the synthesis of alkaline phosphatase as well as that of polyphosphatase without having any effect on pyrophosphatase. The genes phoR and phoS are involved in the formation of a repressory complex both for alkaline phosphatase and polyphosphatase. The gene phoT is probably involved in a partial repression of pyrophosphatase synthesis.

Acid Anhydride Hydrolases↗
PubMed1979

[Phospholipids of E. coli and activity of alkaline phosphatase].

The effects of liposomes prepared from the E. coli lipids on the activity of soluble alkaline phosphatase and on the complementation reaction between its subunits were studied. It was shown that the liposomes nonspecifically catalyze the dimerization of the enzyme subunits without changing the dimer activity. The effects of phospholipases A2 and C on the activity of membrane-bound alkaline phosphatase were studied. An interrelationship was found between the level of hydrolysis of membrane phosphatidyl glycerol (PG) by these enzymes and the changes in the activity of membrane-bound alkaline phosphatase. It was also shown that PG is less accessible to the effects of phospholipases in the cells with derepressed biosynthesis of alkaline phosphatase. It is assumed that the membrane PG interacts with the membrane-bound alkaline phosphatase during its translocation into the periplasm.

Alkaline Phosphatase↗
PubMed1978

[Interrelationship between metabolic and genetic regulation of alkaline and acid phosphatases in E. coli cells].

The effect of exogenous orthophosphate and mutations in regulatory genes of alkaline phosphatase on the level of nonspecific acid phosphatase was studied. The level of this enzyme as well as the level of alkaline phosphatase were shown to be regulated by exogenous orthophosphate being derepressed under phosphate starvation. The derepression of acid phosphatase is accompanied by more rapid secretion of enzyme from membranes to soluble fraction. Mutations in all the four regulatory genes decrease the level of enzyme in cells. Genes phoR and phoS, participating in regulation of alkaline phosphatase, are required for the derepression of acid phosphatase under the conditions of phosphate starvation.

Acid Phosphatase↗
PubMed1978

[Induction of E. coli alkaline phosphatase synthesis in cells preincubated at low temperatures].

Cell preincubation at lowered t degrees was found to result in increased alcaline phosphatase synthesis. The ability of cells for increased alcaline phosphatase synthesis correlates with increased content of cis-vaccinic acid and higher liquidity of lipids. It has been ascertained that modifications caused by cell preincubation at lowered t degrees favour the greater stability of mRNA coding the alcaline phosphatase.

Alkaline Phosphatase↗
PubMed1977

[Phospholipid composition of E. coli cells and membranes under repression and derepression of alkaline phosphatase biosynthesis].

Lipid composition of E. coli membranes and cells in conditions of repression, derepression and constitutive synthesis of alkaline phosphatase is studied. The identity of qualitative composition of phospholipids and neutral lipids in these conditions is demonstrated. Derepressed and constitutive enzyme syntheses are correlating, a certain increase of phosphatidylglycerol in the total phospholipid pool being more pronounced in cells, than in membranes. The enzyme synthesis correlates also with the increase of 14C-label incorporation into lipids.

Alkaline Phosphatase↗
PubMed1976

[Escherichia coli membrane-bound polyphosphatase].

A complex of polyphosphatase with E. coli membranes has been isolated and studied. It is shown by gel-filtration through G-200 Sephadex and centrifugation in sucrose concentration gradient that about 5% of polyphosphatase total content in cells is bound with the heterogenous fraction containing smooth membranes and the ribosome-membrane complex. On the basis of the data obtained it is suggested that the formation of a complex of polyphosphatase with membranes is a stage of synthesis and secretion of this enzyme to protoplasm.

Escherichia coli↗