The primary structure of the initiation factor IF‐3 from <i>Escherichia coli</i>

Brauer, Dieter; Wittmann‐Liebold, Brigitte

doi:10.1016/0014-5793(77)80801-6

Cited by 54 publications

(12 citation statements)

References 31 publications

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“…Another TF, IF3 of E. coli , is known to be methylated at its amino‐terminal residue, Met (Brauer and Wittmann‐Liebold, 1977). The following two different IF3 isoforms are detected during protein purification: the major one, with N ‐monomethylated Met; and the minor one with cleaved Met.…”

Section: Methylation Of Tfs and Hnrnp Proteinsmentioning

confidence: 99%

Methylation of proteins involved in translation

Polevoda¹,

Sherman²

2007

Molecular Microbiology

129

110

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SummaryMethylation is one of the most common protein modifications. Many different prokaryotic and eukaryotic proteins are methylated, including proteins involved in translation, including ribosomal proteins (RPs) and translation factors (TFs). Positions of the methylated residues in six Escherichia coli RPs and two Saccharomyces cerevisiae RPs have been determined. At least two RPs, L3 and L12, are methylated in both organisms. Both prokaryotic and eukaryotic elongation TFs (EF1A) are methylated at lysine residues, while both release factors are methylated at glutamine residues. The enzymes catalysing methylation reactions, protein methyltransferases (MTases), generally use S-adenosylmethionine as the methyl donor to add one to three methyl groups that, in case of arginine, can be asymetrically positioned. The biological significance of RP and TF methylation is poorly understood, and deletions of the MTase genes usually do not cause major phenotypes. Apparently methylation modulates intra-or intermolecular interactions of the target proteins or affects their affinity for RNA, and, thus, influences various cell processes, including transcriptional regulation, RNA processing, ribosome assembly, translation accuracy, protein nuclear trafficking and metabolism, and cellular signalling. Differential methylation of specific RPs and TFs in a number of organisms at different physiological states indicates that this modification may play a regulatory role.

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Section: Methylation Of Tfs and Hnrnp Proteinsmentioning

confidence: 99%

Methylation of proteins involved in translation

Polevoda¹,

Sherman²

2007

Molecular Microbiology

129

110

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“…Fluorescence spectra of labelled and native IF-3 are shown in Fig.3 The identification of peptides was based on maps of IF-3 by Brauer [I61 and Ohsawa (to be published); the nurnbcring of tryptic (T) and Stuphylococcus uureus protease (SP) peptides follows Brauer and Wittmann-Liebold [21]. In both cases the dansylated peptides were poorly soluble, leading to a reduced and presumably biased yield of peptides on the map.…”

Section: Dansyl Chloride Labelling Of If-3mentioning

confidence: 99%

“…A difference in the preference of the two reagents for various exposed lysines is to be expected, since non-covalent association prior to nucleophilic attack will promote the labelling by dansyl chloride of lysines with a nearby apolar surface and that by pyridoxal phosphate of lysines in a region of high local excess positive charge. This suggests, for example, that the positive Nterminal region contains fewer highly apolar residues in its neighbourhood in the folded protein than does the central positive portion of the chain; inspection of the primary structure [21] shows that this could indeed be the case. The significance of this is discussed in the third section of the Results.…”

Section: Dunsylution Of If-3 In the Presence Of 30-s Subunitsmentioning

confidence: 99%

The Binding of Dansylated Initiation Factor 3 to the 30‐S Subunit of Escherichia coli: A Fluorimetric and Biochemical Study

Box

Woolley

Pon

1981

European Journal of Biochemistry

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Initiation factor 3 (IF‐3) has been labelled using dansyl (1‐dimethylaminonaphthalene‐5‐sulphonyl) chloride under conditions designed to preserve the biological activity of the factor. The sites of modification of the IF‐3 have been determined by peptide mapping and sequencing: about six lysines (73, 80, 91, 96, 99, 112) react in various proportions. However, if an IF‐3 molecule bears more than one dansyl group on average then its activity is lost. The extent of incorporation is proportional to the amount of dansyl chloride used in the reaction. Spectrofluorimetric analysis of the dansyl‐IF‐3 leads to the following conclusions. (a) The motion of the dansyl label does not change greatly upon binding to the 30‐S subunit. (b) The label is not close enough to any tryptophan group of the ribosorne in the 30‐S‐subunit · IF‐3 complex to allow energy transfer. (c) The IF‐3 chain is folded so as to bring the tyrosine groups close to the dansyl‐binding sites. (d) The stoichiometry of the binding of IF‐3 to 30‐S ribosomal subunits is close to 1:1 and the binding constant is 2 × 107 M−1. IF‐3 also binds non‐covalently the fluorescent indicator 8‐anilinonaphthalene 1‐sulphonate (ANS) with an apparent binding constant of approximately 8000 M−1. An interaction between ANS and poly(A‐U‐G), both bound to IF‐3. was demonstrated. Combining these results with those for dansyl‐IF‐3 leads to a model for the interaction between IF‐3 and the 30‐S subunit involving a combination of ‘hydrophobic’ and electrostatic attraction between the factor and ribosomal RNA.

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“…9). In fact, the IF3 protein in the cell is found as a mixture of long and short forms (23); the short form is fully active and missing exactly six amino acids from the amino terminus (24). The short form begins with Val-Gln-Thr and thus results from proteolysis (10) rather than translational initiation (through the remnant of the old initiation domain).…”

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confidence: 99%

Escherichia coli translational initiation factor IF3: a unique case of translational regulation.

Gold¹,

Stormo²,

Saunders³

1984

Proc. Natl. Acad. Sci. U.S.A.

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The Escherichia coli translational initiation factor IF3 is encoded by an mRNA that has an unusual ribosome binding site. We have explored a mechanism that may account for the translation of IF3 and that provides regulation of the quantity of IF3 relative to ribosomes.Escherichia coli has many small regulatory loops that tightly control the levels of various important proteins. Such loops often involve regulation of gene expression at the post-transcriptional level (1, 2). In this paper, we propose a regulatory circuit that maintains appropriate levels of the E. coli translational initiation factor IF3 (3). The proposal simultaneously predicts a precise orientation of four different domains of 16S RNA within the 30S ribosomal particle. RESULTS AND DISCUSSIONThe Problem. IF3 is responsible (at least) for dissociating 70S ribosomes that are not making protein, so as to allow the 30S subunit to reengage an mRNA and initiate translation (3). Purified IF3 is required for 70S ribosome dissociation in vitro and for high-level translation of natural mRNAs (3). When a 30S particle, bound to IF3, initiates translation, the normal mechanism is as shown in Fig. 1. Although the nucleotides surrounding initiating codons in E. coli are not random, we do not understand the contribution of that information to the 1000-fold differences in rates of translation between different mRNAs (1, 5, 6). Specifically, we do not know whether any 16S RNA domains (besides the 3' end) are used to achieve mRNA selection. Nevertheless, we have always believed that 16S RNA contains other domains that potentiate mRNA binding, at least for some mRNAs.The sequence of the mRNA encoding the initiation factor IF3 was recently published (7); the translational initiation domain breaks many "rules" followed by most other E. coli mRNAs (1,5,6). The sequence of the IF3 mRNA around the initiation codon is (7) (9). We have attempted to account for IF3 expression by seeking to understand its translation. IF3 expression is known to be regulated. IF3 levels increase, along with the other components of the translational machinery, when growth rates increase (9). That is, E. coli must respond to transiently decreased levels of IF3 by increasing the relative rate of IF3 expression, which is itself needed for the translation of all other mRNAs in the cell. Similarly, excess IF3 should selectively diminish the relative rate of IF3 production. However, IF3 is not feedback regulated by the same mechanism as are ribosomal proteins (2). Cells carrying plasmids encoding IF3 yield more IF3 protein in response to increased plasmid copy number (10).A constant IF3/ribosome ratio could be maintained if IF3 were translated in a mode independent of IF3 function; cells could adjust the relative amount of IF3 made as a result of competition between the IF3 mRNA and all others in the cell. High IF3 levels would stimulate all other mRNAs, leaving few ribosomes for IF3 translation; low IF3 levels would make available many ribosomes for IF3-independent translation of IF3 itsel...

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The primary structure of the initiation factor IF‐3 from Escherichia coli

Cited by 54 publications

References 31 publications

Methylation of proteins involved in translation

Methylation of proteins involved in translation

The Binding of Dansylated Initiation Factor 3 to the 30‐S Subunit of Escherichia coli: A Fluorimetric and Biochemical Study

Escherichia coli translational initiation factor IF3: a unique case of translational regulation.

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