title: Eukaryotic translation initiation factor 5 functions as a GTPase-activating protein.
abstract: Eukaryotic translation initiation factor 5 (eIF5) forms a complex with eIF2 by interacting with the beta subunit of eIF2. This interaction is essential for eIF5-promoted hydrolysis of GTP bound to the 40 S initiation complex. In this work, we show that, in addition to the eIF2 beta-binding region at the C terminus of eIF5, the N-terminal region of eIF5 is also required for eIF5-dependent GTP hydrolysis. Like other GTPase-activating proteins, eIF5 contains an invariant arginine residue (Arg-15) at its N terminus that is essential for its function. Mutation of this arginine residue to alanine or even to conservative lysine caused a severe defect in the ability of eIF5 to promote GTP hydrolysis from the 40 S initiation complex, although the ability of these mutant proteins to bind to eIF2 beta remained unchanged. These mutants were also defective in overall protein synthesis as well as in their ability to support cell growth of a Delta TIF5 yeast strain. Additionally, alanine substitution mutagenesis of eIF5 defined Lys-33 and Lys-55 as also critical for eIF5 function in vitro and in vivo. The implications of these results in relation to other well characterized GAPs are discussed and provide additional evidence that eIF5 functions as a GTPase-activating protein.
authors.affiliation: Department of Developmental and Molecular Biology, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA.
authors.forename: S
authors.initials: S
authors.lastname: Das
authors.forename: R
authors.initials: R
authors.lastname: Ghosh
authors.forename: U
authors.initials: U
authors.lastname: Maitra
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D040061:Eukaryotic Initiation Factor-5; D020690:GTPase-Activating Proteins / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009154:Mutation; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000502:physiology*; D014176:Protein Biosynthesis; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D015852:Eukaryotic Initiation Factor-2; D040061:Eukaryotic Initiation Factor-5; D020690:GTPase-Activating Proteins; D010448:Peptide Initiation Factors; D006160:Guanosine Triphosphate