Febs Letters

1984 Febs Letters

doi: 10.1016/0014-5793(84)81226-0

Agarwal, M.K.

1984 Febs Letters

doi: 10.1016/0014-5793(84)81227-2

Ryazanov, A.G.

1984 Febs Letters

doi: 10.1016/0014-5793(84)81228-4pmid: 6500064

Several aminoacyl‐tRNA synthetases of higher eukaryotes have always been found as multienzyme complexes. There are indications that these complexes can be associated with some tRNA‐modifying enzymes. The function of such complexes is unclear. I have noticed that 6 out of 7 aminoacyl‐tRNA synthetases most commonly occurring in complexes correspond to a group of tRNAs which must always contain a modified U in the first position of their anticodons. A hypothesis is proposed according to which association of 6 aminoacyl‐tRNA synthetases with U‐modifying enzymes can protect a cell from miscoding.

Khananshvili, Daniel; Gromet-Elhanan, Zippora

1984 Febs Letters

doi: 10.1016/0014-5793(84)81229-6

Two ADP binding sites have been demonstrated on the reconstitutively active β‐subunit, that was removed from the Rhodospirillum rubrum membrane‐bound ATP synthase. One is a high affinity site (K d = 0.7 μM) that does not require MgCl2 and is unaffected by it. The second is a low affinity binding site (K d = 80 μM) that is absolutely dependent on MgCl2. For stable binding of ADP to this site, MgCl2 must be present not only during the binding step but also during the elution‐centrifugation step used to separate the β‐subunit bound [3H]ADP from the free ligand. When MgCl2 is removed together with the free ligand [3H]ADP dissociates very rapidly from this second binding site.

Hatch, M.D.; Dröscher, L.; Flügge, U.I.; Heldt, H.W.

1984 FEBS Letters

doi: 10.1016/0014-5793(84)81230-2

Evidence is provided that oxaloacetate is taken up by chloroplasts from maize and spinach leaves by a high‐affinity carrier. Apparent K m values for oxaloacetate are about 45 and 9 μM, respectively. Uptake was measured by following [4‐14C]oxaloacetate reduction in illuminated chloroplasts. With maize chloroplasts the rates of uptake were sufficient to account for photosynthesis. This carrier had a very low affinity for malate and 2‐oxoglutarate. Ratios of the K i, for malate or 2‐oxoglutarate to the K m for oxaloacetate were about 150 and 50, respectively.

Picaud, Serge; Marty, Alain; Trautmann, Alain; Grynszpan-Winograd, Odile; Henry, Jean-Pierre

1984 Febs Letters

doi: 10.1016/0014-5793(84)81231-4pmid: 6500059

Incubation of chromaffin granules with excess liposomes at pH 6.0 resulted in the formation of cell‐size structures, which were purified by centrifugation on sucrose gradients. Experiments with fluorescein‐labeled granules indicated incorporation of granule membrane to these structures. The preparation contained various vesicular structures with a diameter up to 15 μm. The largest elements were studied by the ‘patch‐clamp’ technique. ‘Cell‐attached’ and ‘whole‐cell’ recordings indicated the presence of currents corresponding to unitary conductances ranging from 100 to 500 pS.

Hemilä, Harri; Roberts, Peter; Wikström, Mårten

1984 Febs Letters

doi: 10.1016/0014-5793(84)81232-6pmid: 6094256

Polymorphonuclear leucocytes (PMN) are known to produce Superoxide and other oxygen derivatives upon activation as part of their microbicidal armory. Here we report that extracellular ascorbate is effectively oxidised by activated but not by resting human PMN in vitro. The oxidation of ascorbate is mainly caused by the Superoxide that is generated by the activated cells, as shown by its effective inhibition by Superoxide dismutase. However, myeloperoxidase, which may generate hypochlorite, also contributes to a significant extent. Ascorbate reduces Superoxide to peroxide, as indicated by measurements of the stoichiometry of ascorbate and oxygen consumption. These results support the notion that extracellular ascorbate may serve as an important physiological protecting agent against oxygen radical damage in inflammation.

Kerr, Ellen A.; Yu, Nai-Teng; Gersonde, Klaus

1984 Febs Letters

doi: 10.1016/0014-5793(84)81233-8pmid: 6500060

Resonance Raman (RR) spectra of the monomeric cyanomethaemoglobin CTT III from insect larvae of Chironomus thummi thummi are shown for the range of 200–550 cm−1. By iron and cyanide isotope exchange a line varying between 307 cm−1 for 57Fe‐13C15N and 311 cm−1 for 54Fe‐12C14N, has been assigned to the Fe‐Nϵ stretching mode of this haem complex. The substitution of 54Fe for 57Fe has no effect on the Fe‐C = N bending mode whereas it affects the Fe‐CN stretching mode.

Lavanchy, N.; Martin, J.; Rossi, A.

1984 Febs Letters

doi: 10.1016/0014-5793(84)81234-Xpmid: 6500061

Glycogen synthesis from D‐[1‐13C]glucose was observed in the perfused rat heart by 13C‐NMR spectroscopy at 62.9 MHz. The glycogenogenesis was stimulated by pretreatment of the animals with isoprenaline. Whereas in hearts from control rats the incorporation of D‐[1‐13C]glucose into the glycogen remained below the detection threshold, 5 min proton‐decoupled 13C‐NMR spectra revealed, in hearts from treated rats, a significant labelling of the glycogen within the first minutes of the perfusion and a further linear increase of the glycogen resonance for up to 25 min. This model was used to monitor the appearance of 13C‐labelled lactate during ischemia.

De Marco, Antonio; Zetta, Lucia; Menegatti, Enea; Guarneri, Mario

1984 Febs Letters

doi: 10.1016/0014-5793(84)81235-1

1H‐NMR spectra of Met‐enkephalin dissolved in AOT/isooctane reverse micelles are reported at various temperatures. The NH temperature coefficients are compared with those obtained for the same peptide in normal SDS micelles, in bulk water, and in DMSO. The results show that the opioid molecule undergoes the greatest folding in the reverse micellar system. Shift reagents selectively dissolved in the water pools or in the hydrophobic matrix affect the Phe‐4 or the Tyr‐1 aromatic resonances, respectively. This suggests that the phenylalanyl sidechain is spatially close to the carboxyl group at the C‐terminus, whereas the tyrosyl ring points towards the outer region of the AOT micelles.