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The Role of the Codon and the Initiation Factor IF-2 in the Selection of N-Blocked Aminoacyl-tRNA for Initiation.
- Source :
- European Journal of Biochemistry; 2/15/80, Vol. 104 Issue 1, p19-23, 5p, 4 Graphs
- Publication Year :
- 1980
-
Abstract
- Poly(uridylic acid) [poly(U)] and poly(xanthidylic acid) [poly(X)] strongly stimulate the IF-2-dependent binding of fMet-tRNA to 30-S ribosomal subunits from Escherichia coli [Van der Laken et al. (1979) FEBS Lett. 100, 230–234]. The N-formylmethionine moiety is incorporated into poly(phenylalanine) upon subsequent addition of other components required for protein synthesis when poly(U) is used as template. This paper shows that N-acetylated Phe-tRNA<superscript>Phe</superscript> (AcPhe-tRNA), but not Phe-tRNA<superscript>Phe</superscript> or tRNA<superscript>Phe</superscript>, competes with fMet-tRNA for binding to poly(U)-programmed 30-S ribosomal subunits. The two species of N-blocked aminoacyl-tRNA are bound to poly(U)-programmed and poly(X)-programmed 30-S subunits in a ratio that is linearly dependent on the ratio of the two species added. With poly(U) as template there is no apparent preference for either fMet-tRNA or AcPhe-tRNA, whereas with poly(X) there is a 2–3-fold preference for fMet-tRNA. The initiation factor IF-2, which is strictly required for the binding of N-blocked aminoacyi-tRNAs, has a higher affinity for fMet-tRNA than for AcPhe-tRNA. It is concluded that (a) interaction of the 30-S ribosomal subunit with poly(U) or poly(X) leads to IF-2-dependent binding of N-blocked aminoacyl-tRNA; (b) the initiation factor IF-2 discriminates in favour of fMet-tRNA; (c) the presence of the cognate codon discriminates in favour of the corresponding N-blocked aminoacyl-tRNA. [ABSTRACT FROM AUTHOR]
- Subjects :
- AMINOACYL-tRNA
AMINO acids
TRANSFER RNA
RNA
ESCHERICHIA coli
ESCHERICHIA
Subjects
Details
- Language :
- English
- ISSN :
- 00142956
- Volume :
- 104
- Issue :
- 1
- Database :
- Complementary Index
- Journal :
- European Journal of Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 13616359
- Full Text :
- https://doi.org/10.1111/j.1432-1033.1980.tb04394.x