FEBS Letters

doi: 10.1016/s0014-5793(04)01280-3pmid: N/A

doi: 10.1016/s0014-5793(04)01288-8pmid: N/A

doi: 10.1016/S0014-5793(04)01288-8pmid: N/A

doi: 10.1016/S0014-5793(04)01280-3pmid: N/A

Kuznetsov, Andrey V.; Janakiraman, Manickam; Margreiter, Raimund; Troppmair, Jakob

doi: 10.1016/j.febslet.2004.10.021pmid: 15527752

Cell survival is maintained by growth factors and critically depends on sufficient energy supply. New evidence suggests that a rise in cellular energy production is not merely a homeostatic response to increased demand but subject to regulation by extrinsic factors. The mechanisms operating in this control are largely enigmatic. Work on transformed cells identified direct targeting of glycolytic enzymes by signaling proteins as one possibility. But mitochondrial oxidative phosphorylation and biogenesis may also be subject to regulation by growth and survival factors. Both, positive and negative regulators of cell survival impinge on the processes of cellular energy production to regulate growth and survival versus death.

Schneider, Dirk

doi: 10.1016/j.febslet.2004.10.029pmid: 15527753

The interaction of transmembrane α‐helices is promoted by a detailed fit between two helical surfaces, which results in close packing and van der Waals interactions of amino acid side chains between two helices. Recent studies additionally indicate an important role of hydrogen bonding for mediating and stabilizing transmembrane helix–helix interactions. The interplay between close packing and electrostatic interactions in influencing the specificity of helix–helix interactions on the one hand and the stability of an existing interaction on the other hand is still unknown. Here, we suggest that close packing mainly determines the specificity of a helix–helix interaction, whereas hydrogen bonding is important for stabilization of a preformed helix dimer.

Roosens, Nancy H.; Bernard, Catherine; Leplae, Raphael; Verbruggen, Nathalie

doi: 10.1016/j.febslet.2004.08.084pmid: 15527754

Metallothioneins chelate metals and consequently may be a control point of metal homeostasis. Homologous to type 3 metallothioneins, TcMT3 cDNA was identified in the Cd/Zn hyperaccumulator, Thlaspi caerulescens. TcMT3 amino acid sequence showed modifications in the Cys positions when compared with its Arabidopsis orthologue. A structural model established that the MT3 carboxyterminal domain is similar to the β domain of animal metallothioneins and predicts a smaller cavity to chelate metals for A. thaliana than for T. caerulescens. Functional testing in yeast and Northern blot analysis added further evidence for adaptative variations of MT3 for the maintenance of Cu homeostasis in a metal hyperaccumulator.

Gottfried, Pnina; Kolot, Mikhail; Silberstein, Nava; Yagil, Ezra

doi: 10.1016/j.febslet.2004.09.045pmid: 15527755

Excisionase (Xis) is an accessory protein that is required for the site‐specific excision reaction of the coliphages HK022 and λ. Xis binds in a strong cooperative manner to two tandem binding sites (X1 and X2) located on the P arm of the attachment (att) sites on the phage genome. As a result of crosslinking experiments in vivo and in vitro of Xis‐overexpressing cells, by gel filtration of purified Xis and by FRET analyses we show that Xis monomers of HK022 interact and form dimers that are not dependent on the single Cys residue of the protein and on the presence of DNA. The formation of the dimers may explain the strong binding cooperativity of Xis to its sites on DNA.

Gal, Tali Z.; Glazer, Itamar; Koltai, Hinanit

doi: 10.1016/j.febslet.2004.09.049pmid: 15527756

In order to establish a functional role for late embryogenesis abundant (LEA) proteins in response to stress conditions in Caenorhabditis elegans, we silenced the expression of an LEA (Ce‐lea‐1) gene and determined the survival of worms under stress conditions. Ce‐lea‐1 transcription was induced during dehydration of C. elegans dauer juveniles. Following partial silencing of Ce‐lea‐1 transcription, we demonstrated a specific and significant reduction in worm survival during induction of desiccation, osmotic and heat stress. Together, these results establish a functional role for Ce‐lea‐1 in stress survival of C. elegans and suggest that Ce‐lea‐1 may function as a component that is common to the responses to the examined stress conditions.

Brahma, Amrita; Bhattacharyya, Debasish

doi: 10.1016/j.febslet.2004.09.056pmid: 15527757

UDP‐galactose 4‐epimerase from Kluyveromyces fragilis is a stable homodimer of 75 kDa/subunit with non‐covalently bound NAD acting as cofactor. Partial proteolysis with trypsin in the presence of 5′‐UMP, a strong competitive inhibitor, led to a degraded product which was purified. Results from SDS–PAGE, size‐exclusion (SE)‐HPLC and ultracentrifugation indicated its monomeric status and size between 43 and 45 kDa. `Two‐step assay' with UDP‐glucose dehydrogenase as coupling enzyme in the presence of NAD ensured epimerase activity of the monomer. The possibility of transient dimerization of monomeric epimerase during catalysis was excluded by SE‐HPLC in the presence of excess substrate and NAD. This truncated enzyme retained catalytic site related properties like K m for UDP‐galactose, `NADH‐like coenzyme fluorescence' and `reductive inhibition' similar to its dimeric counterpart. Reversible reactivation of the monomer was achieved up to 95% within 3 min from 8 M urea induced unfolded state, indicating that the catalytic site could form independent of its quaternary structure. Equilibrium unfolding between 0 and 8 M urea indicated that the monomer was less stable compared to the dimer. Chemical modification of amino acids and reconstitution with etheno‐NAD suggested that the architecture around the catalytic site of the monomer was conserved. Specific modification reagents further confirmed that the cysteine residues required for catalysis and coenzyme fluorophore reside exclusively on a single subunit negating a `subunit sharing model' of its catalytic site.