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Prokaryotic initiation factor 2 acts at the level of the 30 S ribosomal subunit
Author(s) -
Gualerzi Claudio O.,
Wintermeyer Wolfgang
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80637-8
Subject(s) - transfer rna , ribosome , initiation factor , ribosomal rna , eukaryotic small ribosomal subunit , p site , chemistry , biochemistry , protein subunit , eukaryotic translation , biology , translation (biology) , rna , messenger rna , gene
The mechanism of action of initiation factor 2 (IF2) from Escherichia coli during initiation of translation was investigated by kinetic analysis of the binding of N ‐AcPhe‐tRNA phe or Phe‐tRNA phe to poly(U)‐programmed 30 S ribosomal subunits. The reaction was studied by using the stopped‐flow technique, monitoring the fluorescence signal of a proflavine inserted next to the anticodon (position 37) of yeast tRNAphe. Both the rate and extent of N ‐AcPhe‐tRNA phe binding to 30 S subunits are strongly enhanced by IF2. The effect of IF2 was studied at different stoichiometric ratios between factor, ribosomes, and N ‐AcPhe‐tRNA phe , in both the presence and absence of the other two factors. In all cases, the IF2 effect titrates with the 30 S ribosomes. This is also the case in the presence of an equimolar amount of 50 S ribosomal subunits. Furthermore, IF2 was found to stimulate strongly the binding of Phe‐tRNA phe , in spite of the inability of the latter to form a detectable binary complex with IF2. The results are interpreted to mean that IF2 acts in a stoichiometric rather than a catalytic fashion, at the level of the 30 S ribosomal subunit. They do not support a model in which IF2 acts as a carrier for the initiator tRNA.