A Novel Form of Initiation Factors from <i>Escherichia coil</i> which Binds Formylmethionyl tRNA and GTP: “F2 · F3 Complex”

Groner, Yoram; Revel, Michel

doi:10.1111/j.1432-1033.1971.tb01525.x

Cited by 40 publications

(7 citation statements)

References 24 publications

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“…8) shows that IF-3 and the IF-2 Wet-tRNA complex counteract each other in binding to the 30-S subunit. It does not support the idea that IF-2 and IF-3 are cooperative in the binding of met-tRNA as was proposed by Groner and Revel [16]. However, the conclusions drawn from their experiments might be wrong because the concentration of IF-3 in the IF-2.…”

Section: Discussioncontrasting

confidence: 50%

Initiation Factor IF-3 and the Binary Complex between Initiation Factor IF-2 and Formylmethionyl-tRNA Are Mutually Exclusive on the 30-S Ribosomal Subunit

Hofstad¹,

Buitenhek²,

Bosch³

et al. 1978

Eur J Biochem

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The formation of 30‐S initiation complexes depends strongly on initiation factor IF‐3; at molar ratios of IF‐3 to 30‐S ribosomes up to one a stimulation is observed, whereas at ratios higher than one, initiation complex formation declines strongly. The target of the observed inhibition of fMet‐tRNA binding at high concentrations of IF‐3 is the 30‐S initiation complex itself. On the one hand addition of IF‐3 to preformed 30‐S initiation complexes leads to a release of bound fMet‐tRNA which is linear with the amount of factor added, whereas no effect on isolated 70‐S initiation complexes is seen. The release of fMet‐tRNA from preformed 30‐S initiation complexes is accompanied by a release of IF‐2 in a one‐to‐one molar ratio which is in agreement with our previous findings showing that binding of fMet‐tRNA takes place via a binary complex: IF‐2 · fMet‐tRNA (Eur. J. Biochem. 66, 181 ‐ 192 and 77, 69–75). On the other hand increasing amounts of both IF‐2 and fMet‐tRNA relieve the IF‐3‐induced inhibition of 30‐S initiation complex formation. From these findings it is concluded that IF‐3 and the IF‐2 · fMet‐tRNA complex are mutually exclusive on the 30‐S ribosome. This implies that under our experimental conditions MS2 RNA binding precedes fMet‐tRNA binding if one accepts that the presence of IF‐3 on the 30‐S subunit is obligatory for messenger binding.

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Section: Discussioncontrasting

confidence: 50%

Initiation Factor IF-3 and the Binary Complex between Initiation Factor IF-2 and Formylmethionyl-tRNA Are Mutually Exclusive on the 30-S Ribosomal Subunit

Hofstad¹,

Buitenhek²,

Bosch³

et al. 1978

Eur J Biochem

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“…A relationship between initiator tRNA and messenger RNA binding has been reported previously in bacterial systems (37)(38)(39). Escherichia coli IF-2, the prokaryotic initiation factor which forms a ternary complex with Met-tRNAf (40)(41)(42), also participates with IF-3 in binding mRNA to the 30S ribosomal subunit (37)(38)(39)(40)(41)(42). The bacterial system does not require poly(A).…”

Section: Methodsmentioning

confidence: 62%

Interaction of poly(A) and mRNA with eukaryotic initiator met-tRNA-f binding factor: identification of this activity on reticulocyte ribonucleic acid protein particles.

Hellerman¹,

Shafritz²

1975

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

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“…After this work was communicated, Groner and Revel (21) reported isolation of an "IF 2. IF 3" fraction that binds GTF and fMet-tRNAf.…”

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confidence: 98%

A Complex Between Initiation Factor IF2, Guanosine Triphosphate, and fMet-tRNA _f : An Intermediate in Initiation Complex Formation

Lockwood

Chakraborty

Maitra

1971

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

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Evidence is presented that suggests the formation of a complex between polypeptide chain-initiation factor IF 2, GTP, and fMet-tRNAf. This complex transfers both fMet-tRNAf and GTP to 30S ribosomal subunits in the presence of ApUpG and initiation factor IF 1. The resultant 30S initiation complex reacts with 50S subunits to form a 70S initiation complex. fMet-tRNAf in this 70S complex reacts with puromycin to form fMet-puromycin.These results suggest that [IF 2, GTP, fMet-tRNAfJ is an intermediate in the initiation of protein synthesis in Escherichia coli.Polypeptide chain initiation in Escherichia coli involves the binding of fMet-tRNAf and mRNA to the 30S ribosomal subunit. A 70S initiation complex is formed when a 50S ribosomal subunit joins the 30S complex (1). Initiation complex formation requires the participation of several protein factors, which can be obtained from ribosomes by washing them with a buffer that contains a high concentration of salt. Reports from various laboratories have described the isolation of three such initiation factors. We have previously designated these factors FI, FIII, and FII in keeping with the order of their elution from DEAE-cellulose columns (2). They appear to correspond to factor F 1, F 2, and F 3 of Ochoa's laboratory (3) and to factors A, B, and C described by Revel and coworkers (4). On the basis of these and other studies (7), it has been suggested that the function of IF 2 in polypeptide chain initiation is similar to that of factor EF G (translocase) in polypeptide chain elongation. Factor EF G catalyzes the GTPdependent movement of nascent peptidyl-tRNA from the acceptor site (A-site) to the donor (puromycin-reactive, P site) (5), It is postulated that IF 2 catalyzes a GTP-dependent translocation of fMet-tRNAf from a site on the 30S ribosome to the donor site on the 70S ribosome, concomitant with the addition of the 50S subunit. GTP would be hydrolyzed to provide energy for this movement.Although such a model has attractive features, IF 2 also has properties analogous to those of elongation factor EF T. Factor EF T catalyzes the binding of aminoacyl-tRNA to ribosomes in the presence of GTP and mRNA. This proceeds through the intermediate formation of an EF T-GTP-aminoacyl tRNA complex (5). EF T factor also catalyzes the hydrolysis of GTP in a reaction dependent on both ribosomal subunits and stimulated by the components necessary for elongation of polypeptide chains (5). Weissbach and coworkers have reported that the initial binding of aminoacyl-tRNA from EF T-GTP-aminoacyl-tRNA may be to the 30S subunit (8).In the studies presented below, we show that IF 2 interacts with GTP in the presence of fMet-tRNAf. Evidence is presented to indicate that this complex is an intermediate in the binding of both fMet-tRNAf and GTP to the 30S subunit. Addition of 50S subunits results in a 70S initiation complex, with fMet-tRNA positioned in the donor site. We suggest that the role of factor IF 2 in polypeptide initiation is analogous to the role of factor EF T in polypep...

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A Novel Form of Initiation Factors from Escherichia coil which Binds Formylmethionyl tRNA and GTP: “F2 · F3 Complex”

Cited by 40 publications

References 24 publications

Initiation Factor IF-3 and the Binary Complex between Initiation Factor IF-2 and Formylmethionyl-tRNA Are Mutually Exclusive on the 30-S Ribosomal Subunit

Initiation Factor IF-3 and the Binary Complex between Initiation Factor IF-2 and Formylmethionyl-tRNA Are Mutually Exclusive on the 30-S Ribosomal Subunit

Interaction of poly(A) and mRNA with eukaryotic initiator met-tRNA-f binding factor: identification of this activity on reticulocyte ribonucleic acid protein particles.

A Complex Between Initiation Factor IF2, Guanosine Triphosphate, and fMet-tRNA _f : An Intermediate in Initiation Complex Formation

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A Novel Form of Initiation Factors from Escherichia coil which Binds Formylmethionyl tRNA and GTP: “F2 · F3 Complex”

Cited by 40 publications

References 24 publications

Initiation Factor IF-3 and the Binary Complex between Initiation Factor IF-2 and Formylmethionyl-tRNA Are Mutually Exclusive on the 30-S Ribosomal Subunit

Initiation Factor IF-3 and the Binary Complex between Initiation Factor IF-2 and Formylmethionyl-tRNA Are Mutually Exclusive on the 30-S Ribosomal Subunit

Interaction of poly(A) and mRNA with eukaryotic initiator met-tRNA-f binding factor: identification of this activity on reticulocyte ribonucleic acid protein particles.

A Complex Between Initiation Factor IF2, Guanosine Triphosphate, and fMet-tRNA f : An Intermediate in Initiation Complex Formation

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A Complex Between Initiation Factor IF2, Guanosine Triphosphate, and fMet-tRNA _f : An Intermediate in Initiation Complex Formation