Reference "Determination of the amino acid sequence of rabbit, human, and wheat germ protein synthesis factor eIF-4C by cloning and chemical sequencing"

Reference ID

9155

Title

Determination of the amino acid sequence of rabbit, human, and wheat germ protein synthesis factor eIF-4C by cloning and chemical sequencing

Source

The Journal of biological chemistry, 1994, vol. 269, pp. 3212-3218

Authors (6)

Dever-T-E	Wei-C-L
Benkowski-L-A	Browning-K
Merrick-W-C	Hershey-J-W

Abstract

The small eukaryotic initiation factor (eIF)-4C is implicated in the initiation
pathway, where it enhances ribosome dissociation into subunits and stabilizes
the binding of the initiator Met-tRNA(i) to 40 S ribosomal subunits. In order to
elucidate the function of eIF-4C, its structure has been further characterized.
The amino acid sequence of many peptides from rabbit reticulocyte and wheat germ
eIF-4C have been determined chemically. From the chemical sequencing of the
rabbit protein, it was noted that at least two different eIF-4C molecules were
present which differed by conservative substitutions at three positions (2
aspartic acid for glutamic acid switches and 1 valine for isoleucine switch). By
the use of unique sequences with low codon degeneracy, primers were used to
obtain a polymerase chain reaction product of appropriate size and sequence.
This product was then used to isolate full-length coding sequence cDNA clones
for human eIF-4C. A similar strategy was used to design PCR primers and then
isolate a wheat cDNA clone which lacked the coding region for the first 23 amino
acids, but contained a complete 3'-untranslated region. The protein amino acid
sequence of wheat germ eIF-4C is 68% identical with the mammalian protein, and,
allowing for the most conservative substitutions, the proteins are 76% similar.
Both the mammalian and wheat germ proteins are 143 amino acids in length and
have molecular weights of about 16,400. A unique feature of eIF-4C is its
apparent "polarity" as 9 of the first 15 amino acids are basic while 13 of the
last 20 amino acids are acidic. This dipole nature may enable the protein to
interact with both the ribosome (perhaps via the rRNA) and other translation
initiation factors.