{PDOC00723}
{PS00938; IF3}
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* Initiation factor 3 signature *
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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).

-Consensus pattern: [KR]-[LIVM](2)-[DN]-[FY]-[GSTN]-[KR]-[LIVMFYS]-x-[FY]-
                    [DEQTAHI]-x(2)-[KRQ]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: December 2001 / Pattern and text revised.

[ 1] Liveris D., Schwartz J.J., Geertman R., Schwartz I.
     "Molecular cloning and sequencing of infC, the gene encoding
     translation initiation factor IF3, from four enterobacterial
     species."
     FEMS Microbiol. Lett. 112:211-216(1993).
     PubMed=8405963
[ 2] Lin Q., Ma L., Burkhart W., Spremulli L.L.
     "Isolation and characterization of cDNA clones for chloroplast
     translational initiation factor-3 from Euglena gracilis."
     J. Biol. Chem. 269:9436-9444(1994).
     PubMed=8144528

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