Febs Letters

doi: 10.1016/0014-5793(89)80878-6pmid: N/A

Matrosovich, Mikhail N.

doi: 10.1016/0014-5793(89)80879-8pmid: 2668026

The development of inhibitors of microbial attachment to target cells has been proposed recently as a possible novel approach to antimicrobial chemoprophylaxis and treatment. In this paper an attempt is made to contend that such artificial inhibitors must be polyvalent, i.e. capable of binding to the pathogen or its target by multiple bonds.

Mauduit, Philippe; Zoukhri, Driss; Rossignol, Bernard

doi: 10.1016/0014-5793(89)80880-4pmid: 2759232

The analysis of the cytosolic fraction from rat exorbital lacrimal gland with DEAE‐cellulose ion‐exchange chromatography showed the presence of a peak of protein kinase activity which was dependent on the presence of phosphatidylserine and diolein as well as calcium. This activity showed the same properties as the previously reported protein kinase C (PKC). Moreover, we have shown for the first time that this kinase or a kinase that coeluted from the column with PKC could be activated by a phorbol ester, PMA, in a phospholipid‐free system, i.e. in the absence of any cofactor of PKC. These findings emphasize the need for caution in the interpretation of experimental results obtained when using phorbol esters to probe for a role of PKC in many regulatory processes.

Zweier, Jay L.; Duke, Scherer S.; Kuppusamy, Periannan; Sylvester, J.T.; Gabrielson, Edward W.

doi: 10.1016/0014-5793(89)80881-6pmid: 2547649

Cells require molecular oxygen for the generation of energy through mitochondrial oxidative phosphorylation; however, high concentrations of oxygen are toxic and can cause cell death. A number of different mechanisms have been proposed to cause cellular oxygen toxicity. One hypothesis is that reactive oxygen free radicals may be generated; however free radical generation in hyperoxic cells has never been directly measured and the mechanism of this radical generation is unknown. In order to determine if cellular oxygen toxicity is free radical mediated, we applied electron paramagnetic resonance, EPR, spectroscopy using the spin trap 5,5′‐dimethyl‐1‐pyrroline‐N‐oxide, DMPO, to measure free radical generation in hyperoxic pulmonary endothelial cells. Cells in air did not give rise to any detectable signal. However, cells exposed to 100% O2 for 30 min exhibited a prominent signal of trapped hydroxyl radical, DMPO‐OH, while cell free buffer did not give rise to any detectable radical generation. This cellular radical generation was demonstrated to be derived from the superoxide radical since the observed signal was totally quenched by superoxide dismutase, but not by equal concentrations of the denatured enzyme. It was confirmed that the hydroxyl radical was generated since in the presence of ethanol the CH3·CH(OH) radical was formed. Loss of cell viability as measured by uptake of trypan blue dye was observed paralleling the measured free radical generation. Thus, superoxide and hydroxyl radicals are generated in hyperoxic pulmonary endothelial cells and this appears to be an important mechanism of cellular oxygen toxicity.

Beauvoit, Bertrand; Rigoulet, Michel; Guerin, Bernard; Canioni, Paul

doi: 10.1016/0014-5793(89)80882-8pmid: N/A

Suspensions of purified yeast mitochondria were analyzed under bubbling oxygen by 31P NMR at 161.9 MHz. The recorded spectra indicate that polyphosphates (poly(P)) are present in mitochondrial preparations. These poly(P) further characterized by the NMR study of mitochondrial perchloric acid extracts have an average chain length of 14 ± 1 residues per chain and correspond to 10% of the total content of cellular poly(P) detected by NMR. The stability of mitochondrial poly(P) was increased by the presence of oligomycin, suggesting that this compound may play a role in the energetic metabolism of yeast mitochondria.

Slijper, M.; Hilbers, C.W.; Konings, R.N.H.; van de Ven, F.J.M.

doi: 10.1016/0014-5793(89)80883-Xpmid: N/A

Nisin is a 34 residue long antimicrobial polypeptide, which contains unusual α,β‐unsaturated amino acids as well as lanthionines. By making use of 2D‐NMR methods, the complete 1H‐NMR spectrum of the polypeptide could be assigned. The NMR data indicate that the molecule adopts a well‐defined three‐dimensional structure.

Chan, Weng C.; Bycroft, Barrie W.; Lian, Lu-Yun; Roberts, Gordon C.K.

doi: 10.1016/0014-5793(89)80884-1pmid: N/A

Two degradation products of nisin have been isolated and their structures have been determined by 1H NMR. Nisin1–32 [(des‐ΔAla33‐Lys34; Val32‐NH2)nisin] and (des‐ΔAla5)nisin1–32 [(des‐ΔAla5, ΔAla33‐Lys34; Ile4‐NH2, pyruvyl‐Leu6, Val32‐NH2)nisin] are formed on storage or by acid treatment. Contrary to previous reports, nisin1–32 showed potent antimicrobial activity against Gram‐positive organisms comparable to that of nisin itself. (des‐ΔAla5)Nisin1–32, however, was biologically inactive, thus demonstrating the importance of ΔAla5 and/or ring A for biological activity.

Toledo, Héctor; Jerez, Carlos A.

doi: 10.1016/0014-5793(89)80885-3pmid: N/A

The role of methylation of elongation factor EF‐Tu from Escherichia coli was investigated. The methylated factor was obtained from cells harvested at the late stationary growth phase. Submethylated forms of the factor were obtained from either bacteria grown to the mid‐logarithmic phase or cells cultured in the presence of ethionine. When fully methylated EF‐Tu was treated in the presence of trypsin, it showed a greatly reduced rate of degradation compared with both types of undermethylated EF‐Tu factors. The methylation of EF‐Tu appeared not to affect the rate of GDP and GTP exchange. However, aminoacyl‐tRNA‐stimulated GTPase activity determined in the presence of kirromycin was greatly increased when the EF‐Tu was methylated.

Koonin, E.V.; Gorbalenya, A.E.; Chumakov, K.M.

doi: 10.1016/0014-5793(89)80886-5pmid: 2759231

Amino acid sequence stretches similar to the four most conserved segments of positive strand RNA viral RNA‐dependent RNA polymerases have been identified in proteins of four dsRNA viruses belonging to three families, i.e. P2 protein of bacteriophage φ6 (Cystoviridae), RNA 2 product of infectious bursa disease virus (Birnaviridae), λ3 protein of reovirus, and VP1 of bluetongue virus (Reoviridae). High statistical significance of the observed similarity was demonstrated, allowing identification of these proteins as likely candidates for RNA‐dependent RNA polymerases. Based on these observations, and on the previously reported sequence similarity between the RNA polymerases of a yeast dsRNA virus and those of positive strand RNA viruses, a possible evolutionary relationship between the two virus classes is discussed.

Blinov, V.M.; Koonin, E.V.; Gorbalenya, A.E.; Kaliman, A.V.; Kryukov, V.M.

doi: 10.1016/0014-5793(89)80887-7pmid: 2547651

It is demonstrated, by computer‐assisted analysis, that T5 bacteriophage early genes D10 and D13 encode proteins containing the purine NTP‐binding sequence motif. The D10 gene product is shown to be a member of a recently characterized superfamily of (putative) DNA and RNA helicases. The D13 gene product is related, at a statistically significant level, to the gene 46 product of bacteriophage T4 which is a component of an exonuclease involved in phage DNA replication, recombination and repair. A lower but also significant degree of sequence similarity was detected between the gene D12 product of T5 and the gene 47 product of T4, the second component of the same nuclease. It is hypothesized that both D10 and D13 gene products of T5 might be NTPases, possibly DNA‐dependent, mediating NTP‐consuming steps during phage DNA replication, recombination and/or repair.