{PDOC00905}
{PS01176; IF2}
{BEGIN}
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* Initiation factor 2 signature *
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Initiation factor  2  (IF-2)  (gene  infB)  [1]  is  one  of the three factors
required  for  the  initiation  of  protein  biosynthesis  in  bacteria.  IF-2
promotes the  GTP-dependent binding of the initiator tRNA to the small subunit
of the  ribosome.  IF-2  is  a  protein  of about 70 to 95 Kd which contains a
central GTP-binding  domain flanked by a highly variable N-terminal domain and
a more conserved C-terminal domain.

Bacterial IF-2   is   structurally  and  functionally  related  to  eukaryotic
mitochondrial  IF-2 (IF-2(mt)) [2] as  well as to algal and plants chloroplast
IF-2 (IF-2(chl)). Both IF-2(mt) and IF-2(chl) are encoded by nuclear genes and
are produced  as  precursor  proteins with a transit peptide. An exception are
red algae where IF-2(chl) is encoded by the plastid genome [3].

As a  signature  pattern,  we  selected  a  conserved region in the C-terminal
section of these proteins.

-Consensus pattern: [GLES]-x-[LIVM]-x(2)-L-[KR]-[KRHNS]-x-K-x(5)-[LIVM]-x(2)-
                    [GNKADS]-x-[DEN]-[CRG]-[GI]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Note: Proteins belonging to this family  also contain a copy  of the ATP/GTP-
 binding motif 'A' (P-loop) (see <PDOC00017>).

-Last update: April 2006 / Pattern revised.

[ 1] Laalami S., Sacerdot C., Vachon G., Mortensen K.,
     Sperling-Petersen H.U., Cenatiempo Y., Grunberg-Manago M.
     "Structural and functional domains of E coli initiation factor IF2."
     Biochimie 73:1557-1566(1991).
     PubMed=1805969
[ 2] Ma L., Spremulli L.L.
     "Cloning and sequence analysis of the human mitochondrial
     translational initiation factor 2 cDNA."
     J. Biol. Chem. 270:1859-1865(1995).
     PubMed=7829522
[ 3] Kostrzewa M., Zetsche K.
     "Organization of plastid-encoded ATPase genes and flanking regions
     including homologues of infB and tsf in the thermophilic red alga
     Galdieria sulphuraria."
     Plant Mol. Biol. 23:67-76(1993).
     PubMed=8219057

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