The N-terminal extension of the ADP/ATP translocator is not involved in targeting to plant mitochondria in vivo

The mitochondrial ADP/ATP translocator, also called adenine nucleotide translocase (ANT), is synthesized in plants with an N-terminal extension which is cleaved upon import into mitochondria. In contrast, the homologous proteins of mammals or fungi do not contain such a transient amino terminal presequence. To investigate whether the N-terminal extension is needed for correct intracellular sorting in vivo , translational fusions were constructed of the translocator cDNA—with and without presequence—with the β-glucuronidase ( gus ) reporter gene. The distribution of reporter enzymatic activity in the subcellular compartments of transgenic plants and transformed yeast cells was subsequently analysed. The results show that: (i) the plant translocator presequence is not necessary for the correct localization of the ANT to the mitochondria; (ii) the mitochondrial targeting information contained in the mature part of the protein is sufficient to overcome, to some extent, the presence of plastid transit peptides; and (iii) the presequence alone is not able to target a passenger protein to mitochondria in vivo .     

Beta-2 microglobulin types in mice of wild origin

To determine the distribution of beta-2 microglobulin (B2m) alleles in wild mice we have typed mice derived from natural populations in Europe, North Africa, South America, and East Asia. Mus musculus domesticus mice from Germany, France, Italy, and Peru were all B2m ^a as were most from the United Kingdom. M.m. musculus mice from Denmark and Czechoslovakia, several stocks of M.m. molossinus from Japan, and M.m. castaneus from China, Thailand, and the Philippines were of B2m ^b type. This is consistent with the notion that C57BL/6 may have obtained some of its genes, including B2m, from Eastern mice. A BgII restriction site characteristic of B2m ^b was also found in mice from Czechoslovakia and Japan, confirming that B2m ^b is a naturally occurring allele of B2m. A new type of ₂m ( ₂m^w1) was found in four stocks of M. spretus from Portugal, Spain, and Morocco. This molecule differs in apparent size and charge from the a and b types. ₂m^w2 was found together with ₂ ma in one stock of M.m. domesticus (brevirostris) from Morocco. ₂m^w3 and ₂m^w4 were found in a few M. m. bactrianus from Pakistan. In all cases tested, these new ₂m molecules associate with class I histocompatibility antigens.Abbreviations used in this paper ₂m beta-2 microglobulin - B2m gene for beta-2 microglobulin - IEF isoelectric focusing - SDS-PAGE polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate - MHC major histocompatibility complex - T. E. Tris-EDTA buffer     

Isolation and characterization of the outer membrane of Acinetobacter calcoaceticus

A method for the separation of the outer membrane (OM) from the cytoplasmic membrane (CM) of Acinetobacter calcoaceticus 69/V grown on different carbon sources is described. The contamination of the OM with CM was less than 10%. Independent of the carbon source, five protein bands with apparent molecular weights of 47 000, 33000, 21 000, 19 000 and 12 000 were found by solubilization at 37°C and six bands at 100°C (apparent M_r 53 000, 47 000, 38 000, 26 000, 21000, 12000). Three proteins were modifiable by heat. With the periodic acid-Schiff procedure the bands with apparent M_r of 33 000 and 12 000 were made visible. After growth on d,l-carnitine an additional two non-heat-modifiable protein bands with apparent M_r between 40 000 and 45 000 were detected. By cultivation on acetate and peptone as carbon source one additional band (M_r 15 000) from OM of cells could be found.     

Uptake, release and metabolism of docosahexaenoic acid (DHA, c22:6 omega 3) in human platelets and neutrophils

Exogenous DHA is converted by human platelets to 14- and 11- HDHE and by human neutrophils mainly to 7- HDHE . Human platelets prelabeled with 14C-DHA, 14C-EPA and 14C-AA and stimulated with thrombin release and metabolize DHA only in trace amounts as compared to EPA and AA. 14C-DHA is incorporated into the 2-position of platelet phospholipids and occurs predominantly in phosphatidylethanolamine. DHA and EPA were also incorporated by dietary means into phospholipids of platelets and neutrophils. In resting platelets free DHA as well as free AA and EPA are not detectable. In platelets stimulated ex vivo with thrombin DHA is not significantly released which is in contrast to EPA and AA. After stimulation, 14- HDHE is found only in trace amounts as compared to 12-HETE and 12- HEPE . In DHA enriched neutrophils formation of HDHEs cannot be demonstrated after stimulation with ionophore A 23187. We conclude that even after dietary enrichment of DHA in phospholipids of platelets and neutrophils the level of free DHA and/or formation of HDHEs might be too low to substantially affect arachidonic acid metabolism and related functions of these cells.     

Enhanced casein kinase II activity in human tumour cell cultures

Casein kinase II (CKII) activity is enhanced as much as 2–3 fold in established and 4–5-fold in transformed human cell lines when compared to that of fibroblasts and primary human tumour cell cultures where CKII activity never exceeded a basic level. The high activity of CKII in transformed cells and in established cell lines was reduced to about the same basic level after treatment with heparin, a highly specific inhibitor of CKII activity. The activity of the cAMP-dependent protein kinase was virtually the same in fibroblasts and various human tumour cell lines investigated.     

Resolution of optical isomers by high-pressure liquid chromatography: The separation of benzo[a]pyrene trans-diol derivatives

The optical isomers of (±)r-7,t-8-dihydroxy-7,8-dihydrobenzo[a]pyrene and its synthetic precursor (±)r-7,t-8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene were resolved as their di-(−)menthoxyacetates using high-pressure liquid chromatography. Saponification of the resolved diesters yielded the corresponding enantiomers. The specific rotation, CD spectra, and ORD curves are reported. The resolution of these optical isomers permits detailed studies on the enzymatic intermediates and the mechanism of benzo[a]pyrene activation to its carcinogenic form. The method is of general usefulness for the resolution of optical isomers.     

Germacranolides from Melampodium americanum and Melampodium pilosum

Chemical analysis of Melampodium americanum yielded, besides the known melampodinin A, four new melampolides, melampodinin B, melampodinin C, 9-des     

The carbonyl reactivity of 3-bromopyruvate and related compounds

The covalent hydration of β-halopyruvic acids and β-halopyruvamides has been investigated in the uv region by stopped-flow techniques. In aqueous solutions of β-bromopyruvate and related compounds, the geminal diol is the predominant form at all pH values. Kinetic investigations have also been carried out on these hydrations. General bases enhance the rate of approaching the equilibrium. Specific acid catalysis was not detected. In the water-catalyzed reaction of pyruvamides, the relationship between the equilibrium constants K and the rate constants of the forward reaction shows that the transition state is more productlike.