Phosphorylation of mammalian translation initiation factor 5 (eIF5) in vitro and in vivo
AUTOR(ES)
Majumdar, Romit
FONTE
Oxford University Press
RESUMO
Eukaryotic translation initiation factor 5 (eIF5) interacts with the 40S initiation complex (40S•eIF3•AUG•Met-tRNAf•eIF2•GTP) and, acting as a GTPase activating protein, promotes the hydrolysis of bound GTP. We isolated a protein kinase from rabbit reticulocyte lysates on the basis of its ability to phosphorylate purified bacterially expressed recombinant rat eIF5. Physical, biochemical and antigenic properties of this kinase identify it as casein kinase II (CK II). Mass spectrometric analysis of maximally in vitro phosphorylated eIF5 localized the major phosphorylation sites at Ser-387 and Ser-388 near the C-terminus of eIF5. These serine residues are embedded within a cluster of acidic amino acid residues and account for nearly 90% of the total in vitro eIF5 phosphorylation. A minor phosphorylation site at Ser-174 was also observed. Alanine substitution mutagenesis at Ser-387 and Ser-388 of eIF5 abolishes phosphorylation by the purified kinase as well as by crude reticulocyte lysates. The same mutations also abolish phosphorylation of eIF5 when transfected into mammalian cells suggesting that CK II phosphorylates eIF5 at these two serine residues in vivo as well.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=101238Documentos Relacionados
- Mutational Analysis of Mammalian Translation Initiation Factor 5 (eIF5): Role of Interaction between the β Subunit of eIF2 and eIF5 in eIF5 Function In Vitro and In Vivo
- Cloning and characterization of the p42 subunit of mammalian translation initiation factor 3 (eIF3): demonstration that eIF3 interacts with eIF5 in mammalian cells.
- A multifactor complex of eukaryotic initiation factors, eIF1, eIF2, eIF3, eIF5, and initiator tRNAMet is an important translation initiation intermediate in vivo
- Dominant negative mutants of mammalian translation initiation factor eIF-4A define a critical role for eIF-4F in cap-dependent and cap-independent initiation of translation.
- Mutations in the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2 alpha) that overcome the inhibitory effect of eIF-2 alpha phosphorylation on translation initiation.