Further evidence on the role of the A protein in bacteriophage MS2 particles

Verbraeken, E; Fiers, Walter

doi:10.1016/0014-5793(72)80684-7

Cited by 7 publications

(1 citation statement)

References 14 publications

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“…For cells labeled in the presence of polyamine, this peak was estimated to contain some 15% as much radioactivity as did A protein in the same gel. Assuming that the preparation of phage proteins put on the gel contained 180 or more [39] times as many coat protein molecules as molecules of A protein, that coat was extracted twice as efficiently from the gel as was A protein, and knowing A protein to have five histidine residues then the number of histidine residues erroneously incorporated per coat protein molecule would be less than or equal to 2 x w3.…”

Section: Specific Activity Of Amino Acids Within Cellmentioning

confidence: 99%

Effect of polyamines on translation fidelity in vivo

McMurry

Algranati

1986

European Journal of Biochemistry

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Polyamines, when added to cell-free protein-synthesizing systems, have been shown either to reduce mistranslation or to increase it depending upon the composition of the reaction mixture. To study this question under conditions as natural as possible we investigated the effects of polyamines on the fidelity of protein synthesis in intact Escherichiu coli bacterial cells, using strains which were auxotrophic for polyamine synthesis. Error was measured in two ways: (a) the incorporation of [3H]histidine into coat protein of bacteriophage MS2, the gene of which does not code for histidine, and (b) the synthesis of a basic variant of MS2 coat protein in which a lysine erroneously replaces an asparagine, causing a change in isoelectric point. We found that when cell cultures were supplemented with polyamines there was no effect on the first type of error and the second type decreased twofold. The measured errors occurred at the level of translation because their frequency increased in the presence of streptomycin and decreased in cells bearing a streptomycin-resistance mutation known to lower the occurrence of translational misreading. The average erroneous incorporation per mol coat protein in the presence of polyamines was 1.43 ? 0.59 mmol histidine and 25 -34 mmol lysine/asparagine substitution. The reason for the different effect of polyamines on the two types of error is not known but could be related to the difference between their corresponding frequencies or to codon-specific effects.Polyamines are widely distributed organic cations which appear to have many roles, especially in processes involving nucleic acids, such as DNA replication, transcription and translation [I -51. Studies carried out with cell-free systems have demonstrated that polyamines can replace part of the magnesium requirement of protein synthesis and at the same time cause overall stimulation [6 -81. Polyamines have also been shown to have a qualitative effect on the proteins synthesized. Adenovirus proteins made in vitro in the presence of polyamines resembled more closely those synthesized in vivo, both in size and quantity [9]. Polypeptides of higher molecular mass were found in smaller amounts in the absence of polyamines in vitro [lo, 111 and in vivo [12]. These observations had suggested that polyamines might prevent premature peptide termination or otherwise affect the fidelity of translation. It was subsequently reported that polyamines, particularly spermidine, decreased the misincorporation of leucine for phenylalanine severalfold in a polyuridylic-acid-dependent in vitro translation system [13-151. However, in these studies the error determinations in presence of polyamines were done at lower Mg concentrations than those in the absence of polyamines because the Mg optimum for polyphenylalanine synthesis was higher under the latter conditions than in the presence of polyamines. In one study, other changes besides polyamine addition were made [16]. At some concentrations of Mg, however, the error was no different or [18] that when...

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Section: Specific Activity Of Amino Acids Within Cellmentioning

confidence: 99%