Prokaryotic initiation factor 2 acts at the level of the 30 S ribosomal subunit

FEBS Letters

Gualerzi, Claudio O.¹  Wintermeyer, Wolfgang¹ 

[1] Max-Planck-Institutfür Molekulare Genetik, Abteilung Wittmann, Ihnestrasse 73, D-1000 Berlin 33 Dahlem, Germany

关键词: Protein synthesis Initiation factor Stopped-flow kinetics Fluorescence;   

DOI  :  10.1016/0014-5793(86)80637-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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.

【 授权许可】

Unknown