Functional groups of elongation factor 2 involved in interactions with guanosine nucleotides and ribosomes

Nurten, Rüstem; Aktar, Neş'e Bilgin; Bermek, Engin

doi:10.1016/0014-5793(83)80189-6

Cited by 9 publications

(3 citation statements)

References 15 publications

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“…Using this technique the unmodified factor was found to be approximately 100 times more efficient in forming a complex with the ribosome than the phosphorylated factor (Table 2). Due to the presence of functionally essential amino groups in eEF-2 [34], the fixation is likely to interfere with both the association and dissociation rates during the fixation period. The dissociation constants determined by this method could therefore be too low if the dissociation rate is reduced much more by the fixation than the rate of association.…”

Section: Resultsmentioning

confidence: 99%

Functional properties of phosphorylated elongation factor 2

Carlberg

Nilsson

Nygård

1990

European Journal of Biochemistry

253

197

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The effect of phosphorylation on the functional activity of eukaryotic elongation factor 2 (eEF-2) was studied using a purified phosphorylated factor. The modified factor was unable to stimulate protein synthesis in an eEF-2-dependent rabbit reticulocyte lysate. The functional alteration was further analyzed by measuring the effects of phosphorylation on the ability of the factor to catalyse the ribosome-dependent hydrolysis of GTP. Kinetic analysis showed that both phosphorylated and unmodified factor was able to hydrolyse GTP with approximately the same maximum rate, indicating that the rate of nucleotide exchange was not impaired by the modification. However, the phosphorylated factor showed a marked reduction in the second-order rate constant, suggesting that the phosphorylation interfered with ribosome . eEF-2 complex formation by reducing the affinity of eEF-2 for the ribosome. This assumption was confirmed by direct measurements of the dissociation constants for the ribosomal complexes containing unmodified and phosphorylated eEF-2.

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Section: Resultsmentioning

confidence: 99%

Functional properties of phosphorylated elongation factor 2

Carlberg

Nilsson

Nygård

1990

European Journal of Biochemistry

253

197

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“…GSH has been shown to exert a regulatory effect by enzyme activation through mixed disulfide formation (enzyme-S-thiolation) (Ziegler, 1985). Influence at the transcriptional level through inhibition of eF-2 is also a possibility (Nurten et al, 1983;Sutter and Muldave, 1966) but further study will be required to clarify the mechanism of these agents in altering the course of redifferentiation in hepatocyte monolayers.…”

Section: Discussionmentioning

confidence: 99%

Cystathionase activity and glutathione metabolism in redifferentiating rat hepatocyte primary cultures

Meredith

1987

Cell Biol Toxicol

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Capacity to incorporate methionine sulfur into glutathione as well as cystathionase activity were lost in cultured hepatocytes in a biphasic manner with 75% of the total capacity disappearing with a half-life of about 10.6 hr, the remainder with a half-life of greater than 20 hr. Nicotinamide, 25 mM, produced a single phase loss with a t 1/2 of approximately 21 hr for both transsulfuration and cystathionase activity. Loss of both methionine sulfur incorporation and cystathionase activity occurred in transferrin/sodium selenite-supplemented Williams Medium E (TS-HWME) with a t 1/2 of about 96 hr through 72 hr in culture. Addition of the cystathionase inhibitor, propargylglycine, blocked glutathione synthesis in TS-HWME cells through 48 hr in culture, while propargylglycine blocked glutathione synthesis only at 4 hr in HWME cultured cells. Further, the accumulation of gamma-glutamyl transpeptidase was delayed by 48 hr in TS-HWME versus unsupplemented medium. Variation in the transport of sulfur amino acids was also found to occur with culture age. The Km values for cysteine and methionine transport were found to be approximately 150 and 100 microM, respectively, and were unaffected by culture age or the presence of TS-HWME. However, the Vmax for transport of methionine declined from 0.29 to 0.012 nmol/min/mg protein over 48 hr in culture. In TS medium, the Vmax at 48 hr for methionine transport had only decreased to 0.20 nmol/min/mg protein and increased for cysteine transport to 0.17 nmol/min/mg protein. These data suggest that during the redifferentiation of hepatocytes in culture, transsulfuration is regulated by control of the flow of substrate through cystathionase and that cystathionase is regulated by alteration of enzyme activity or content. Variations in the rate of transport of precursor sulfur amino acids are also an important component of the regulation of the net glutathione status of the redifferentiating hepatocyte.

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“…GTP . ribosome complexes without an apparent loss of the guanosine nucleotide binding ability [221], indicating that the cysteine residues are essential for ribosome binding. However, as the cysteines are scattered over the whole molecule, this experiment does not show which parts of the molecule that are involved in the ribosome interaction.…”

Section: Interaction Of Eef-2 With Ribosomesmentioning

confidence: 99%