Isolation and purification of Mn-peroxidase from Azospirillum brasilense SP245

Homogenous Mn-peroxidase of a 26-fold purity grade was isolated from a culture of Azospirillum brasilense Sp245 cultivated on a medium containing 0.1 mM pyrocatechol. The molecular weight of the enzyme is 43 kD as revealed by electrophoresis in SDS-PAAG. It was shown that the use of pyrocatechol and 2,2′-azino-bis(3-ethylbenzotiazoline-6-sulfonate) at concentrations of 0.1 and 1 mM as inductors increased the Mn-peroxidase activity by a factor of 3.     

Effect of apoptotic proteins on function of rat vasopressin-and dopaminergic hypothalamic neurons

To study character of effect of apoptotic signal proteins on activities of neurosecretory cells and neurons of rat hypothalamus, pharmacological inhibitors of proapoptotic protein p53 Pifithrin-α and antiapoptotic protein Bcl-2 HA14-1 were injected into hypothalamus. Activation of vasopressinergic neurosecretory cells at administration of the blocker Bcl-2 HA14-1 was shown: there were observed an increase of vasopressin mRNA in neurons of hypothalamic supraoptical and paraventricular nuclei, a decrease of the immunoreactive vasopressin content in posterior pituitary, and reduction of diuresis. Inactivation of p53 inhibited release of vasopressin from hypothalamus cell bodies, which is indicated by an elevated content of immunoreactive vasopressin in neurosecretory cell bodies with its unchanged synthesis, a decrease of the neurohormone content in the posterior pituitary, and an increase of diuresis rate. Activation of vasopressinergic neurons of the suprachiasmatic nucleus was also shown. Administration of the blocker of Bcl-2 has been revealed to decrease functional activity both of dopaminergic neurons (zona incerta) and of dopaminergic neurosecretory cells (arcuate nucleus), in which a decrease of the tyrosine hydroxylase content was observed. The p53 inactivation also led to a decrease of activity of dopaminergic neurosecretory cells of arcuate nucleus, whereas activity of the neurons of zona incerta did not change. Thus, it has been shown that a change of the apoptotic protein content in vasopressinergic and dopaminergic neurons and neurosecretory cells leads to a change of their functional activity, the character and possibly mechanisms of effects of apoptotic proteins on activities of vasopressin-and dopaminergic cells being different.     

Rett syndrome-causing mutations in human MeCP2 result in diverse structural changes that impact folding and DNA interactions

Most cases of Rett syndrome (RTT) are caused by mutations in the methylated DNA-binding protein, MeCP2. Here, we have shown that frequent RTT-causing missense mutations (R106W, R133C, F155S, T158M) located in the methylated DNA-binding domain (MBD) of MeCP2 have profound and diverse effects on its structure, stability, and DNA-binding properties. Fluorescence spectroscopy, which reports on the single tryptophan in the MBD, indicated that this residue is strongly protected from the aqueous environment in the wild type but is more exposed in the R133C and F155S mutations. In the mutant proteins R133C, F155S, and T158M, the thermal stability of the domain was strongly reduced. Thermal stability of the wild-type protein was increased in the presence of unmethylated DNA and was further enhanced by DNA methylation. DNA-induced thermal stability was also seen, but to a lesser extent, in each of the mutant proteins. Circular dichroism (CD) of the MBD revealed differences in the secondary structure of the four mutants. Upon binding to methylated DNA, the wild type showed a subtle but reproducible increase in alpha-helical structure, whereas the F155S and R106W did not acquire secondary structure with DNA. Each of the mutant proteins studied is unique in terms of the properties of the MBD and the structural changes induced by DNA binding. For each mutation, we examined the extent to which the magnitude of these differences correlated with the severity of RTT patient symptoms.     

Intracellular lectins of Lentinus edodes at various developmental stages of the fungus

A number of lectins varying in polypeptide composition and carbohydrate specificity were isolated from Lentinus edodes at different stages of its morphogenesis: nonpigmented mycelium, brown mycelium film, and fruiting body. Three lectins were identified at the nonpigmented mycelium stage, two of them being dimers consisting of 16 and 45 kDa and 16 and 42 kDa subunits; the third is a tetramer of 16, 39, 42, and 45 kDa subunits. The fractions with lectin activity obtained at the brown mycelium film stage contained polypeptides of 24, 30, and 38 kDa, characteristic of this morphological structure. The fruiting body was shown to contain two lectins of 43 and 55 kDa. All of the isolated lectins expressed the highest affinity towards L,D-melibiose, D-lactose, and D-galactose.     

Enzymes of the xylotrophic basidiomycete Lentinus edodes F-249 in the course of morphogenesis

It has been shown that the fungus Lentinus edodes grown on a solid wort agar substrate produces intracellular enzymes, including Mn-dependent peroxidase, laccase, and tyrosinase as a family of isoforms. The composition of the complex (containing one to four forms of each enzyme) varied during the basidiomycete life cycle. The activity of oxidases was maximal at the stage of nonpigmented mycelium and at the stages of a brown mycelial mat and a fruit body. The activity of tyrosinase increased in the course of mycelium pigmentation and had two maxima: at the stage of a brown mycelial mat and at the stage of a fruit body. Laccase and tyrosinase activities were shown to increase sharply upon addition of oak sawdust extract to the culture medium as compared with the enzyme activities of mycelium grown on wort agar alone. It was established that the effect of phenol oxidase substrates on the growing mycelium consists in a twofold acceleration of the process of morphogenesis in the fungus L. edodes.     

Effect of Azospirilla Lectins on Germination Capacity of Seeds

We studied the effect of lectins of Azospirillum brasilense Sp 7 on germination capacity of tomato, cucumber, pea, wheat, and onion seeds. The lectins proved to inhibit seed germination. We studied the effect of different concentrations of lectins from four azospirilla strains on the rate of wheat seed germination. Both inhibiting and stimulating effects were demonstrated. Lectin-induced changes in the mitotic state of plant cells were demonstrated with histological sections of the root growing point in onion.     

Semidominant Effect of the l(1)ts403 (sbr 10) Mutation on Sex Chromosome Nondsjunction in Meiosis in Drosophila melanogaster Females Exposed to Heat

The sbrgene of Drosophila melanogasterbelongs to the NXF(nuclear export factor) family responsible for the mRNA transport from nucleus to cytoplasm. We have shown that in the heat-exposed (37°C, 1 h) females, the l(1)ts403(sbr ¹⁰) mutation leads, in particular, to the high-frequency nondisjunction and loss of sex chromosomes in meiosis. For this trait, the incomplete dominance of the sbr ¹⁰ mutation is observed. At the same time, the sbr ¹⁰ mutation is recessive for many other traits of the heat-exposed flies: reduced viability, low fertility, impaired synthesis of the heat shock proteins, etc. The females heterozygous for the null allele (Df(1)v ^L4, a deletion eliminating gene srb) do not differ from females homozygous for the wild-type allele in frequency of the heat shock-induced nondisjunction and loss of sex chromosomes in meiosis. Because of this, the sbr ¹⁰ mutation can be assigned to the gain-of-function alleles (those gaining the dominance function). Expression of the mutant sbr ¹⁰ allele against the background of the wild-type allele suggests that in the heat shock-exposed females, the heat-modified product of this ts allele has an active effect on sex chromosome disjunction in meiosis.