Identification and purification of GTP-binding regulatory proteins from plasma membranes of swine heart

A 23 kDa GTP-binding protein was purified from pig heart sarcolemma. This protein was not ADP-ribosylated by cholera, pertussis and botulinum C3 toxins. In pig heart sarcolemma pertussis toxin ADP-ribosylated 40 kDa subunit of Gi-protein, cholera toxin--45 kDa subunit of Gs-protein, botulinum C3 toxin ADP-ribosylated a group of proteins with Mr 22, 26 and 29 kDa. Antiserum generated against the peptide common for all alpha-subunits of G-proteins did not react with purified 23 kDa protein. Trypsin cleaved the 23 kDa protein in the presence of guanyl nucleotides into a 22 kDa fragment. Proteolysis of the 39 kDa alpha 0-subunit from bovine brain plasma membranes and ADP-ribosylated 40 kDa alpha i-subunit from pig heart sarcolemma in the presence of GTP gamma S yielded the 37 and 38 kDa fragments, respectively. In the presence of GTP and GDP the proteolysis of alpha 0 yielded the 24 and 15 kDa fragments, while the proteolysis of ADP-ribosylated alpha i-subunit yielded a labelled 16 kDa peptide. Irrespective of nucleotides trypsin cleaved the ADP-ribosylated 26 kDa substrate of botulinum C3 toxin into two labelled peptides with Mr 24 and 17 kDa. The data obtained indicate the existence in pig heart sarcolemma of a new 23 kDa GTP-binding protein with partial homology to the alpha-subunits of "classical" G-proteins.     

A physiological role for DNA supercoiling in the anaerobic regulation of colicin gene expression

Summary The mechanism of anaerobic regulation of synthesis of colicins E1, E2, E3, K and D was studied. It was found that anaerobiosis significantly increases expression of the genes for colicins E1, E2, E3, K, and D. Experiments with novobiocin (a DNA gyrase inhibitor) showed that colicin synthesis in minicells and derepressed colicin synthesis in cells are dramatically reduced by relaxation of DNA supercoiling. A good correlation was observed between the levels of colicin synthesis and plasmid DNA supercoiling and the degree of aeration of the cultures. Thus, the regulation of colicin gene expression in response to a change in aeration appears to be mediated by environmentally induced variations in DNA supercoiling.     

The stability of the alkylating derivatives of oligodeoxyribonucleotides containing a cholesterol or phenazine radical added to the 3'-termination during their interaction with Acholeplasma laidlawii PG-8]

Stability of alkylating derivatives of decathymidylates protected on the 3'-terminal by cholesterol and phenazine residues has been studied in the process of their interaction with cells of Acholeplasma laidlawii PG-8. It is shown that the studied reagents are not split by nucleases of A. laidlawii PG-8 for the time necessary for alkylation of mycoplasma biopolymers.     

Interaction between the mitochondrial ATP synthetase and ATPase inhibitor protein. Active/inactive slow pH-dependent transitions of the inhibitor protein

The rate of mitochondrial ATPase inactivation by the naturally occurring inhibitor protein in the presence of saturating ATP and Mg2+ at pH 8.0 depends hyperbolically on the amount of inhibitor added; the upper limit of an apparent first-order constant for the inactivation process is 1.0(-1) at 25 degrees C. A dramatic difference in the inactivation rate is observed when the protein inhibitor is added to the same assay system from either acidic (pH 4.8) or alkaline (pH 8.2) solutions. The slow reversible transition of the inhibitor from its rapidly reacting 'acidic' form to the slow reacting 'alkaline' form occurs when the solution of the protein inhibitor is subjected to a pH-jump from 4.8 to 8.2 (t1/2 approximately 30s at 25 degrees C). The pH-profile of the inhibitor active/inactive equilibrium suggests that a group with pKa approximately 6.5 is involved in the transition. Treatment of the inhibitor protein with a histidine-specific reagent (e.g. diethyl pyrocarbonate) abolishes its inactivating effect on the ATPase activity. It is concluded that the protonation/deprotonation of the inhibitor protein followed by its slow conformational changes is the rate-limiting step in the inhibitor-ATP synthetase interaction.     

Guanine nucleotide-dependent, pertussis toxin-insensitive regulation of phosphoinositide turnover by bradykinin in bovine pulmonary artery endothelial cells

In this paper we examine the effect of the vasodilator peptide bradykinin on endothelial cell regulation of phosphoinositide (PI) turnover. The data show that the activation of PI turnover by bradykinin in bovine pulmonary artery endothelial cells is insensitive to pertussis toxin, which ADP ribosylates a membrane protein of mol wt 40,000. However, this effect of bradykinin can be potentiated by guanosine 5'-O-(3-thio)triphosphate (GTP gamma S), an activator of G proteins, and depressed by guanosine 5'-O-(2-thio)diphosphate (GDP beta S), an inhibitor of G proteins. After endothelial cells were preincubated for 1 h with GTP gamma S, there was a three- to fourfold increase in PI turnover. Preincubation of cells with GDP beta S did not affect the basal level of PI turnover, but completely prevented activation of PI turnover by bradykinin. 4 beta-Phorbol-12 beta-myristate-13 alpha-acetate can block the bradykinin-stimulated inositol monophosphate formation in cultured endothelial cells. The effects of bradykinin on PI turnover were blocked by B2 antagonists but not by B1 antagonists. Taken together, these results indicate that in endothelial cells the bradykinin B2 receptor is coupled to phospholipase C via a G protein (or proteins) that is not a substrate for pertussis toxin (neither Gi nor Go).     

Genetic differentiation in a captive population of the endangered Siberian crane (Grus leucogeranus Pall.)

DNA fingerprinting, followed by multivariate analysis of data, was used to characterize genetic heterogeneity in captive populations of the endangered Siberian and sandhill cranes. The genetic structure revealed reflected the natural population and species distributions. The relevant groups differed not only from each other, but also from interspecies and inter-population hybrids bred in captivity. In this study we have tested an approach to the analysis of population structure based on individual genotypes. Interpretation of fingerprinting data by means of the analytical system applied here is a useful and reliable procedure for the estimation of genetic relationships between individuals.     

Effect of apomorphine on rat brain opiate receptors

Stereospecific binding of apomorphine to rat brain opiate receptors was shown by assaying the competition of 7,8(n)--3H--naloxone and D-ala2-tyrosyl-3,5-3H--enkephalin (5-D-leucine) for opiate receptor binding. EC-NaCl50, the concentration of apomorphine which inhibited 50% binding of the radioactive naloxone and D-ala2, D-leu5-enkephalin in the absence of NaCl were 20 and 42 microM, respectively. EC+NaCl 50, the concentration of apomorphine which inhibited 50% binding of the radioactive naloxone in the presence of 100 mM NaCl was 17 microM. From the ratio of EC+NaCl 50 to EC-NaCl the value of "sodium shift" of effective concentration can be calculated as 0.85. From the data obtained it is concluded that apomorphine, like naloxone, is a "pure" antagonist but it has much less affinity for enkephalin and opiate binding sites. The probable mechanisms of the pharmacological action of apomorphine are discussed.     

Diffuse and Volume Discharges in High-Pressure Gas Lasers Pumped by Transverse Discharge (A Review)

Plasma Physics Reports - Consideration is given to the formation of conditions and parameters of diffuse and volume discharges, which are widely used for laser generation in VUV, UV, visible and IR...