PROSITE documentation PDOC00723
Initiation factor 3 signature


Initiation factor 3 (IF-3) (gene infC) [1] is one of the three factors required for the initiation of protein biosynthesis in bacteria. IF-3 is thought to function as a fidelity factor during the assembly of the ternary initiation complex which consist of the 30S ribosomal subunit, the initiator tRNA and the messenger RNA. IF-3 binds to the 30S ribosomal subunit; it is a basic protein of 141 to 212 residues.

The chloroplast initiation factor IF-3(chl) is a protein that enhances the poly(A,U,G)-dependent binding of the initiator tRNA to chloroplast ribosomal 30s subunits. In its mature form it is a protein of about 400 residues whose central section is evolutionary related to the sequence of bacterial IF-3 [2].

As a signature pattern we selected a highly conserved region located in the central section of bacterial IF-3 and of IF-3(chl).

Last update:

December 2001 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

IF3, PS00938; Initiation factor 3 signature  (PATTERN)


1AuthorsLiveris D. Schwartz J.J. Geertman R. Schwartz I.
TitleMolecular cloning and sequencing of infC, the gene encoding translation initiation factor IF3, from four enterobacterial species.
SourceFEMS Microbiol. Lett. 112:211-216(1993).
PubMed ID8405963

2AuthorsLin Q. Ma L. Burkhart W. Spremulli L.L.
TitleIsolation and characterization of cDNA clones for chloroplast translational initiation factor-3 from Euglena gracilis.
SourceJ. Biol. Chem. 269:9436-9444(1994).
PubMed ID8144528

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