Stoicheiometry of dicyclohexylcarbodiimide-ATPase interaction in mitochondria

1. The oligomeric dicyclohexylcarbodiimide (DCCD)-binding protein of mitochondrial ATPase was studied using (a) the relationship between [¹⁴C]DCCD binding and inhibition of ATPase activities and (b) the analysis of the kinetics of inhibition. 2. The [¹⁴C]DCCD binding to bovine heart mitochondria is linearly proportional to the inhibition of ATP hydrolysis up to a 50% decrease of the original activity resulting in 0.6 mol DCCD bound covalently to the specific inhibitory site (Hous?t?k, J., Svoboda, P., Kopecký, J., Kuz?ela, S?. and Drahota, Z. (1981) Biochim. Biophys. Acta 634, 331–339) per mol of the fully inhibited enzyme. 3. Kinetics of the inhibition of both the ATPase activity (heart and liver mitochondria) and ADP-stimulated respiration (liver) reveal that 1 mol DCCD per mol ATPase eliminates both the synthetic and the hydrolytic activities. It is inferred that the activity-binding correlation underestimates the number of DCCD-reactive sites. 4. The second-order rate constant of the DCCD-ATPase interaction (k) is inversely related to the concentration of membranes, indicating that DCCD reaches the inhibitory site by concentrating in the hydrophobic (phospholipid) environment. 5. At a given concentration of liver mitochondria, comparable k values are obtained both for the inhibition of ATP hydrolysis (k=5.35·10²M^?1·min^?1) and ADP-stimulated respiration (k=5.67·10²M^?1·min^?1). 6. It is concluded that both the synthetic and the hydrolytic functions of ATPase are inhibited via a common single DCCD-reactive site. This site is represented by one of the several polypeptide chains forming the oligomer of the DCCD-binding protein. The inhibitor-ATPase interaction does not exhibit cooperativity, indicating that the preferential reactivity towards DCCD is an inherent property of the inhibitory site.     

Disulfide-bonded discontinuous epitopes on the glycoprotein of vesicular stomatitis virus (New Jersey serotype).

Intrachain disulfide bonds between paired cysteines in the glycoprotein (G) of vesicular stomatitis virus (VSV) are required for the recognition of discontinuous epitopes by specific monoclonal antibodies (MAbs) (W. Keil and R. R. Wagner, Virology 170:392-407, 1989). Cleavage by Staphylococcus aureus V8 protease of the 517-amino-acid VSV-New Jersey G protein, limited to the glutamic acid at residue 110, resulted in a protein (designated GV8) with greatly retarded migration by polyacrylamide gel electrophoresis (PAGE) under nonreducing conditions. By Western blot (immunoblot) analysis, protein GV8 was found to lose discontinuous epitope IV, which maps within the first 193 NH2-terminal amino acids. These data, coupled with those obtained by PAGE migration of a vector-expressed, truncated protein (G1-193) under reducing and nonreducing conditions, lead us to postulate the existence of a major loop structure within the first 193 NH2-terminal amino acids of the G protein, possibly anchored by a disulfide bond between cysteine 108 and cysteine 169, encompassing epitope IV. Site-directed mutants in which 10 of the 12 cysteines were individually converted to serines in vaccinia virus-based vectors expressing these single-site mutant G proteins were also constructed, each of which was then tested by immunoprecipitation for its capacity to recognize epitope-specific MAbs. These results showed that mutations in NH2-terminal cysteines 130, 174, and, to a lesser extent, 193 all resulted in the loss of neutralization epitope VIII. A mutation at NH2-terminal cysteine 130 also resulted in the loss of neutralization epitope VII, as did a mutation at cysteine 108 to a lesser extent. Both epitopes VII and VIII disappeared when mutations were made in COOH-distal cysteine 235, 240, or 273, the general map locations of epitopes VII and VIII. These studies also reveal that distal, as well as proximal, cysteine residues markedly influence the disulfide-bond secondary structure, which ostensibly determines the conformational structure of the VSV-New Jersey G protein required for presentation of the major discontinuous epitopes recognized by neutralizing MAbs.     

Glycoprotein IV of bovine herpesvirus 1-expressing cell line complements and rescues a conditionally lethal viral mutant.

Glycoprotein IV (gIV) of bovine herpesvirus 1 (BHV-1), a homolog of herpes simplex virus glycoprotein D, represents a major component of the viral envelope and a dominant immunogen. To analyze the functional role of gIV during BHV-1 replication, cell line BUIV3-7, which constitutively expresses gIV, was constructed and used for the isolation of gIV- BHV-1 mutant 80-221, in which the gIV gene was replaced by a lacZ expression cassette. On complementing gIV-expressing cells, the gIV- BHV-1 replicated normally but was unable to form plaques and infectious progeny on noncomplementing cells. Further analysis showed that gIV is essential for BHV-1 entry into target cells, whereas viral gene expression, DNA replication, and envelopment appear unchanged in both noncomplementing and complementing cells infected with phenotypically complemented gIV- BHV-1. The block in entry could be overcome by polyethylene glycol-induced membrane fusion. After passaging of gIV- BHV-1 on complementing cells, a rescued variant, BHV-1res, was isolated and shown to underexpress gIV in comparison with its wild-type parent. Comparison of the penetration kinetics of BHV-1 wild type, phenotypically complemented gIV- BHV-1, and BHV-1res indicated that penetration efficiency correlated with the amount of gIV present in virus particles. In conclusion, we show that gIV of BHV-1 is an essential component of the virion involved in virus entry and that the amount of gIV in the viral envelope modulates the penetration efficiency of the virus.     

Spinally-mediated antinociception is induced in mice by an adenosine kinase-, but not by an adenosine deaminase-, inhibitor.

Relative involvement of adenosine deaminase and adenosine kinase in antinociception induced by endogenous adenosine was investigated. Antinociception induced by 5'-amino 5'-deoxyadenosine (5'-ADAdo; an adenosine kinase inhibitor) and deoxycoformycin (dCF; an adenosine deaminase inhibitor) administered i.t. was determined using the mouse tail-flick assay. Dose- and time-dependent antinociception was observed following i.t. administration of 5'-ADAdo, but not dCF. Antinociception induced by 5'-ADAdo was reversed by coadministration i.t. of theophylline, an adenosine receptor antagonist, in a dose-dependent manner. These data provide preliminary evidence that adenosine kinase plays a more significant physiological role than adenosine deaminase in the regulation of adenosine involved in spinally-mediated antinociception.     

Oenanthe aquatica (L.)Poir.: Seed reproduction,population structure,habitat conditions and distribution in Czechoslovakia

The paper summarizes data concerning the biology and ecology ofOenanthe aquatica. The species is commonly distributed all over Czechoslovakia, from lowlands to the submontane belt, especially in fishpond and river basins.O. aquatica shows no special relationship to the chemical and physical soil properties, and is well adapted to habitats with a changing water level. The reproduction ofO. aquatica depends on emerging of the bottom. The most developed populations are formed by biennial plants and arise in the year following summer or autumn drainage.     

Effect of dehydration on thirst and drinking during immersion in men.

The mechanism for reduced voluntary water intake during water immersion was studied in eight men (19-25 yr of age) immersed to the neck while sitting for 3 h at 34.5 degrees C or in air at 28 degrees C when euhydrated (Eu-H2O and Eu-air, respectively) and hypohydrated (Hypo-H2O and Hypo-air) by 3.6% body weight loss. Thirst sensations (degree of thirst, mouth dryness and taste, drinking desirability, and stomach fullness) were similar at the beginning of Hypo-air and Hypo-H2O test periods. Initial drinking of tap water (15 degrees C) was 216 +/- 30 ml/7 min (P less than 0.05) with Hypo-air, decreased to 108 +/- 28 ml/7 min (P less than 0.05) with Hypo-H2O, and was 10-50 ml/10-30 min thereafter. Intake was less than 10 ml/10-30 min in Eu-air, and there was no drinking in Eu-H2O. Within the first 10 min of immersion, compared with Hypo-air findings, the significant reduction in drinking in the Hypo-H2O experiment was associated with unchanged plasma Na+, plasma osmolality, heart rates, and mean arterial pressures; the different responses were increased cardiac output, plasma volume, and atrial natriuretic peptides and decreased plasma renin activity and arginine vasopressin. Thus the extracellular pathway, as opposed to the osmotic pathway, appears to be the major mechanism for immersion-induced suppression of drinking.     

Gene expression during tuber development in potato plants

Potato tubers are modified stems that have differentiated into storage organs. Factors such as day-length, nitrogen supply, and levels of the phytohormones cytokinin and gibberellic acid, are known to control tuberization. Morphological changes during tuber initiation are accompanied by the accumulation of a characteristic set of proteins, thought to be involved in N-storage (i.e. patatin) or defense against microbial or insect attack (i.e. proteinase inhibitor II). Additionally, deposition of large amounts of starch occurs during tuber formation, which is paralleled by an increase in sucrose synthase and other enzymes involved in starch biosynthesis (i.e. ADP-glucose pyrophosphorylase, starch synthases, and branching enzyme). Potential controlling mechanisms for genes expressed during tuberization are discussed.