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Eukaryotic translation initiation factor 5 (elF5) acts as a classical GTPase-activator protein

Eukaryotic translation initiation factor 5 (elF5) acts as a classical GTPase-activator protein
Eukaryotic translation initiation factor 5 (elF5) acts as a classical GTPase-activator protein
GTP hydrolysis occurs at several specific stages during the initiation, elongation, and termination stages of mRNA translation. However, it is unclear how GTP hydrolysis occurs; it has previously been suggested to involve a GTPase active center in the ribosome, although proof for this is lacking. Alternatively, it could involve the translation factors themselves, e.g., be similar to the situation for small G in which the GTPase active site involves arginine residues contributed by a further protein termed a GTPase-activator protein (GAP). During translation initiation in eukaryotes, initiation factor eIF5 is required for hydrolysis of GTP bound to eIF2 (the protein which brings the initiator Met-tRNAi to the 40S subunit). Here we show that eIF5 displays the hallmarks of a classical GAP (e.g., RasGAP). Firstly, its interaction with eIF2 is enhanced by AlF4?. Secondly, eIF5 possesses a conserved arginine (Arg15) which, like the “arginine fingers” of classical GAPs, is flanked by hydrophobic residues. Mutation of Arg15 to methionine abolishes the ability of eIF5 either to stimulate GTP hydrolysis or to support mRNA translation in vitro. Mutation studies suggest that a second conserved arginine (Arg48) also contributes to the GTPase active site of the eIF2.eIF5 complex. Our data thus show that eIF5 behaves as a classical GAP and that GTP hydrolysis during translation involves proteins extrinsic to the ribosome. Indeed, inspection of their sequences suggests that other translation factors may also act as GAPs.
0960-9822
55-59
Paulin, F.E.M.
5e142441-db4d-41d1-ba03-0f6c8c59fe5b
Campbell, L.E.
c7fd39f9-947a-4bc2-af95-3f5b5670b7fd
Brien, K.
2b9fa9b3-9fbe-4a2a-8c53-ae439e3ee374
Loughlin, J.
f54ed02a-0402-4f56-b494-bbe90f9aff08
Proud, C.G.
c2cc50f9-4565-4d59-9dfc-aa70b9268a6e
Paulin, F.E.M.
5e142441-db4d-41d1-ba03-0f6c8c59fe5b
Campbell, L.E.
c7fd39f9-947a-4bc2-af95-3f5b5670b7fd
Brien, K.
2b9fa9b3-9fbe-4a2a-8c53-ae439e3ee374
Loughlin, J.
f54ed02a-0402-4f56-b494-bbe90f9aff08
Proud, C.G.
c2cc50f9-4565-4d59-9dfc-aa70b9268a6e

Paulin, F.E.M., Campbell, L.E., Brien, K., Loughlin, J. and Proud, C.G. (2001) Eukaryotic translation initiation factor 5 (elF5) acts as a classical GTPase-activator protein. Current Biology, 11 (1), 55-59. (doi:10.1016/S0960-9822(00)00025-7).

Record type: Article

Abstract

GTP hydrolysis occurs at several specific stages during the initiation, elongation, and termination stages of mRNA translation. However, it is unclear how GTP hydrolysis occurs; it has previously been suggested to involve a GTPase active center in the ribosome, although proof for this is lacking. Alternatively, it could involve the translation factors themselves, e.g., be similar to the situation for small G in which the GTPase active site involves arginine residues contributed by a further protein termed a GTPase-activator protein (GAP). During translation initiation in eukaryotes, initiation factor eIF5 is required for hydrolysis of GTP bound to eIF2 (the protein which brings the initiator Met-tRNAi to the 40S subunit). Here we show that eIF5 displays the hallmarks of a classical GAP (e.g., RasGAP). Firstly, its interaction with eIF2 is enhanced by AlF4?. Secondly, eIF5 possesses a conserved arginine (Arg15) which, like the “arginine fingers” of classical GAPs, is flanked by hydrophobic residues. Mutation of Arg15 to methionine abolishes the ability of eIF5 either to stimulate GTP hydrolysis or to support mRNA translation in vitro. Mutation studies suggest that a second conserved arginine (Arg48) also contributes to the GTPase active site of the eIF2.eIF5 complex. Our data thus show that eIF5 behaves as a classical GAP and that GTP hydrolysis during translation involves proteins extrinsic to the ribosome. Indeed, inspection of their sequences suggests that other translation factors may also act as GAPs.

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Published date: 1 January 2001

Identifiers

Local EPrints ID: 56020
URI: http://eprints.soton.ac.uk/id/eprint/56020
ISSN: 0960-9822
PURE UUID: c8e5eb77-6e21-473a-aacd-d78829606160

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Date deposited: 07 Aug 2008
Last modified: 15 Mar 2024 10:59

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Contributors

Author: F.E.M. Paulin
Author: L.E. Campbell
Author: K. Brien
Author: J. Loughlin
Author: C.G. Proud

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