eIF4E, Protein Synthesis Initiation Factor 4E
Source: Recombinant human produced in E. coli.
Purity: > 90% by SDS-PAGE, apparent Mr ~ 28-kDa (see figure below).
Supplied: In 50 μl of 50 mM Tris-HCl pH 7.0 buffer containing 14 mM β-mercaptoethanol, 1 mM benzamidine, 0.1 mM phenylmethanesulfonyl fluoride, 1 mM EDTA and 10% glycerol. Maintain in aliquots at -70° C. Avoid repeated thawing.
Synonyms: Eukaryotic Protein Synthesis Initiation Factor 4E; eIF-4E
Background: The mRNA Cap-binding protein synthesis initiation factor 4E (eIF4E) participates in an early rate limiting step in protein synthesis. Over-expression of eIF4E leads to cell transformation and tumorigenesis and occurs in a number of cancer cells. eIF4E occurs as an inactive complex with the 4EBP binding proteins in quiescent cells. However, in response to insulin and other extracellular stimuli, eIF4E dissociates from 4EBP and is recruited to the active eIF4F complex. In addition to eIF4E, the eIF4F complex contains eIF4A and eIF4G. In cells exposed to insulin and other growth factors, eIF4E is phosphorylated at Ser209. The affinity of eIF4E to capped mRNA is enhanced by this phosphorylation, which is catalyzed by Mitogen-Activated Protein Kinase (MAPK) Interacting Kinases (Mnk’s). It is also catalyzed by an insulin-stimulated protein kinase termed cPK which also phosphorylates Thr210 on the initiation factor.
Figure: SDS-PAGE pattern of a purified preparation of eIF4E (28 kDa). The gel was stained with Coomassie Blue.
References: J Biol Chem 270, 14824-14828; J Biol Chem 270, 14597-14603; Biochime 76, 822-830; J Biol Chem 271, 11831-11837; J Biol Chem 270, 21684-21688
