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Initiation factor IF 2 binds to the α-sarcin loop and helix 89 of Escherichia coli 23S ribosomal RNA

Published online by Cambridge University Press:  27 July 2001

ANNA LA TEANA ,
CLAUDIO O. GUALERZI  and
ALBERT E. DAHLBERG
ANNA LA TEANA
Affiliation:
Insitute of Biochemistry, University of Ancona, 60131 Ancona, Italy
CLAUDIO O. GUALERZI
Affiliation:
Laboratory of Genetics, Department of Biology MCA, University of Camerino, 62032 Camerino (MC), Italy
ALBERT E. DAHLBERG
Affiliation:
J.W. Wilson Laboratory, Department of Molecular & Cell Biology and Biochemistry, Brown University, Providence, Rhode Island 02912, USA
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Abstract

During initiation of protein synthesis in bacteria, translation initiation factor IF2 is responsible for the recognition of the initiator tRNA (fMet-tRNA). To perform this function, IF2 binds to the ribosome interacting with both 30S and 50S ribosomal subunits. Here we report the topographical localization of translation initiation factor IF2 on the 70S ribosome determined by base-specific chemical probing. Our results indicate that IF2 specifically protects from chemical modification two sites in domain V of 23S rRNA, namely A2476 and A2478, and residues around position 2660 in domain VI, the so-called sarcin-ricin loop. These footprints are generated by IF2 regardless of the presence of fMet-tRNA, GTP, mRNA, and IF1. IF2 causes no specific protection of 16S rRNA. We observe a decreased reactivity of residues A1418 and A1483, which is an indication that the initiation factor has a tightening effect on the association of ribosomal subunits. This result, confirmed by sucrose density gradient analysis, seems to be a universally conserved property of IF2.

Keywords

ribosomal topographyrRNA functionsubunit associationtranslation initiation
Type
Research Article
Information
RNA , Volume 7 , Issue 8 , August 2001 , pp. 1173 - 1179
Copyright
© 2001 RNA Society

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