Muhammet Bektaş

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Different lines of evidence indicate that eukaryotic elongation factor 2 (eEF2) can be ADP-ribosylated endogenously. The physiological significance of this reaction has, however, remained unclarified. In order to address this issue we investigated the in vivo ADP-ribosylation of eEF2 and the effect of oxidative stress thereon. The investigation revealed(More)
Eukaryotic elongation factor 2 (EF-2) was shown to bind to F-actin as assayed by co-sedimentation. In the presence of guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) binding was increased fourfold. At saturation level a molar ratio of about 0.12 EF-2 per F-actin (subunit) was observed. Our results suggest a single type of binding site with an apparent(More)
Interactions of elongation factor 2 (EF-2) with G-actin and F-actin in vitro were investigated using viscosimetry, gel filtration and electron microscopy. Under depolymerization conditions, at a molar ratio of 0.5:1 (EF-2/F-actin subunit), F-actin is stabilised by EF-2 and filaments depolymerize about three times slower than control solutions containing(More)
An inhibitor of diphtheria toxin- and endogenous transferase-dependent ADP-ribosylation of eukaryotic elongation factor 2 (eEF2) has been found in the cytoplasmic fraction from rat liver. We provide evidence that this cytoplasmic inhibitor corresponds to actin, which gives rise also to inhibition of polyphenylalanine (polyPhe) synthesis. Both globular(More)
It was shown by gel filtration and viscosity measurements that N-terminal fragment (FA) of diphtheria toxin (DT) can interact with both G- and F-actin (filamentous actin). Elution profiles on Sephadex G-100 indicated the formation of a binary complex of fragment A (FA) with globular actin monomer (G-actin), which was inhibited by gelsolin. Deoxyribonuclease(More)
Eukaryotic elongation factor 2 can undergo ADP-ribosylation in the absence of diphtheria toxin under the action of an endogenous transferase. The investigation which aimed to gain insight into the nature of endogenous ADP-ribosylation revealed that this reaction may be, in some cases, due to covalent binding of free ADP-ribose to elongation factor 2.(More)
Diphtheria toxin has been well characterized in terms of its receptor binding and receptor mediated endocytosis. However, the precise mechanism of the cytosolic release of diphtheria toxin fragment A from early endosomes is still unclear. Various reports differ regarding the requirement for cytosolic factors in this process. Here, we present data indicating(More)
Diphtheria toxin (DT) and its N-terminal fragment A (FA) catalyse the transfer of the ADP-ribose moiety of nicotinamide adenine dinucleotide (NAD) into a covalent linkage with eukaryotic elongation factor 2 (eEF2). DT-induced cytotoxicity is versatile, and it includes DNA cleavage and the depolymerisation of actin filaments. The inhibition of the(More)
– Let () , M g be a compact immersed hypersurface of () 1 , , n R + < > , 1 λ the first nonzero eigenvalue, α the mean curvature, ρ the support function, A the shape operator, () vol M the volume of M, and S the scalar curvature of M. In this paper, we established some eigenvalue inequalities and proved the above. 1) 2 2 22 1 M M A dv dv n ρ αρ ≥ ∫ ∫ , 2)(More)
Eukaryotic elongation factor 2 (eEF-2) can undergo ADP-ribosylation in the absence of diphtheria toxin. The binding of free ADP-ribose and endogenous transferase-dependent ADP-ribosylation were distinct reactions for eEF-2, as indicated by different findings. Incubation of eEF-2 tryptic fragment 32/33 kDa (32F) with NAD was ADP-ribosylated and gave rise to(More)