The role of IF-3 in the translation of T7-and ϕ80trp messenger RNA

✍ Scribed by Benne, Rob ;Pouwels, Peter H.

• Book ID: 104693315
• Publisher: Springer
• Year: 1975
• Tongue: English
• Weight: 575 KB
• Volume: 139
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00267971

✦ Synopsis

The DNA dependent synthesis of proteins was studied with a system composed of DNA, washed ribosomes, centrifuged (150,000 X g) bacterial extract from Escherichia coli and purified initiation factors IF-1 and IF-2. Synthesis of active enzymes encoded by the tryptophan (trp)-operon of E. coli was found to depend strongly on the addition of IF-3, with the same IF-3 dependency for all 5 gene-products of this operon, irrespective of the presence of the promotor proximal gene trpE. Synthesis of T7 RNA polymerase with T7 DNA as a template, however, was completely independent of the addition of IF-3. The same difference in IF-3 requirement was found when we compared the overall protein synthesis directed by these templates. This difference could be related to the effect of IF-3 on the formation of initiation complexes with the in vitro prepared mRNA: initiation complexes are readily formed with T7 mRNA also in the absence of IF-3, whereas the formation of these complexes with phi80trp mRNA almost completely depends on the presence of this factor.