Is eIF2 a GTPase?

Is eIF2 a GTPase?

Pathway Description: Upon AUG recognition, eIF2 hydrolyzes GTP to GDP with the help of the GTPase activating protein eIF5 and dissociates from the mRNA, permitting the binding of the 60S ribosomal subunit and elongation of the polypeptide chain.

What is the purpose of eIF2 binding to GTP?

eIF2 plays a central role in the maintenance of what is generally considered a rate-limiting step in mRNA translation. In this step, eIF2 binds GTP and Met-tRNAi and transfers Met-tRNAi to the 40S ribosomal subunit. At the end of the initiation process, GTP bound to eIF2 is hydrolyzed to GDP and the eIF2.

What is eIF2 signaling?

Eukaryotic Initiation Factor 2 (eIF2) Signaling Regulates Proinflammatory Cytokine Expression and Bacterial Invasion.

What is the role of eIF2 in the Preinitiation complex?

eIF2 is the main protein complex responsible for delivering the initiator tRNA to the P-site of the preinitiation complex, as a ternary complex containing Met-tRNAiMet and GTP (the eIF2-TC).

How is eIF2 regulated?

eIF2 activation is highly regulated. In response to a wide range of signals, multiple protein kinases phosphorylate a single serine, historically known as Ser51, within the eIF2α subunit. This inhibits the GEF activity of eIF2B forming a tight eIF2αP/eIF2B inhibitory complex3,9,10.

What is eIF2 phosphorylation?

Phosphorylated eIF2 acts as a dominant inhibitor of the guanine nucleotide exchange factor eIF2B and prevents the recycling of eIF2 between successive rounds of protein synthesis.

What does phosphorylation of eIF2 do?

What is the key role that eIF2B plays in translation?

eIF2B is a multisubunit protein that is critical for protein synthesis initiation and its control. It is a guanine nucleotide exchange factor (GEF) for its GTP-binding protein partner eIF2. eIF2 binds initiator tRNA to ribosomes and promotes mRNA AUG codon recognition.

Is eIF2 a G protein?

Eukaryotic translation initiation factor 2 (eIF2) is a G protein heterotrimer required for GTP-dependent delivery of initiator tRNA to the ribosome.

Which of the following would be the initiator tRNA for protein?

One of the most widespread beliefs in molecular biology is that protein synthesis is initiated with methionine or formylmethionine in all organisms, by using AUG as the initiation codon and a special methionine tRNA called the initiator tRNA (1, 2).

What is the function of eIF2 in translation?

It is required for most forms of eukaryotic translation initiation. eIF2 mediates the binding of tRNA iMet to the ribosome in a GTP -dependent manner. eIF2 is a heterotrimer consisting of an alpha (also called subunit 1, EIF2S1), a beta (subunit 2, EIF2S2), and a gamma (subunit 3, EIF2S3) subunit.

Which subunits of eIF2 are involved in the hydrolysis of GTP?

Following the association of mRNA with the 40S subunit and location of the subunit at the AUG start codon, eIF5 binds to eIF2 and stimulates the hydrolysis of eIF2-bound GTP. It has been proposed that either eIF5 or the β- or γ-subunits of eIF2 contains the GTPase activity responsible for GTP hydrolysis.

What is eIF2 (eukaryotic initiation factor)?

Eukaryotic initiation factor eIF2 originally was identified over 25 years ago as a protein that bound GTP and initiator methionyl-tRNA i (Met-tRNA i) and mediated the association of Met-tRNA i to the 40S ribosomal subunit (reviewed in [1] ).

Why is eIF2 an inhibitor of its own GEF (eIF2B)?

Phosphorylated eIF2, however, due to its stronger binding, acts as an inhibitor of its own GEF (eIF2B). Since the cellular concentration of eIF2B is much lower than that of eIF2, even a small amount of phosphorylated eIF2 can completely abolish eIF2B activity by sequestration.