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Characterization of the mammalian initiation factor eIF2B complex as a GDP dissociation stimulator protein

Characterization of the mammalian initiation factor eIF2B complex as a GDP dissociation stimulator protein
Characterization of the mammalian initiation factor eIF2B complex as a GDP dissociation stimulator protein
Initiation factor eIF2B mediates a key regulatory step in the initiation of mRNA translation, i.e. the regeneration of active eIF2·GTP complexes. It is composed of five subunits, -. The largest of these () displays catalytic activity in the absence of the others. The catalytic mechanism of eIF2B and the functions of the other subunits remain to be clarified. Here we show that, when present at similar concentrations to eIF2, mammalian eIF2B can mediate release of eIF2-bound GDP even in the absence of free nucleotide, indicating that it acts as a GDP dissociation stimulator protein. Consistent with this, addition of GDP to purified eIF2·eIF2B complexes causes them to dissociate. The alternative sequential mechanism would require that eIF2B itself bind GTP. However, we show that it is the -subunit of eIF2B that interacts with GTP. This indicates that binding of GTP to eIF2B is not an essential element of its mechanism. eIF2B preparations that lack the -subunit display reduced activity compared with the holocomplex. Supplementation of such preparations with recombinant eIF2B markedly enhances activity, indicating that eIF2B is required for full activity of mammalian eIF2B.
0021-9258
24697-24703
Williams, D.D.
1428b355-db6e-4a92-9c49-38a888c8f9ef
Price, N.T.
8d2f5709-fd5c-4091-97fd-d08bfbce2e44
Loughlin, A.J.
d522d1c1-34c5-400b-9be9-5d5a9110ed9b
Proud, C.G.
c2cc50f9-4565-4d59-9dfc-aa70b9268a6e
Williams, D.D.
1428b355-db6e-4a92-9c49-38a888c8f9ef
Price, N.T.
8d2f5709-fd5c-4091-97fd-d08bfbce2e44
Loughlin, A.J.
d522d1c1-34c5-400b-9be9-5d5a9110ed9b
Proud, C.G.
c2cc50f9-4565-4d59-9dfc-aa70b9268a6e

Williams, D.D., Price, N.T., Loughlin, A.J. and Proud, C.G. (2001) Characterization of the mammalian initiation factor eIF2B complex as a GDP dissociation stimulator protein. The Journal of Biological Chemistry, 276 (27), 24697-24703. (doi:10.1074/jbc.M011788200).

Record type: Article

Abstract

Initiation factor eIF2B mediates a key regulatory step in the initiation of mRNA translation, i.e. the regeneration of active eIF2·GTP complexes. It is composed of five subunits, -. The largest of these () displays catalytic activity in the absence of the others. The catalytic mechanism of eIF2B and the functions of the other subunits remain to be clarified. Here we show that, when present at similar concentrations to eIF2, mammalian eIF2B can mediate release of eIF2-bound GDP even in the absence of free nucleotide, indicating that it acts as a GDP dissociation stimulator protein. Consistent with this, addition of GDP to purified eIF2·eIF2B complexes causes them to dissociate. The alternative sequential mechanism would require that eIF2B itself bind GTP. However, we show that it is the -subunit of eIF2B that interacts with GTP. This indicates that binding of GTP to eIF2B is not an essential element of its mechanism. eIF2B preparations that lack the -subunit display reduced activity compared with the holocomplex. Supplementation of such preparations with recombinant eIF2B markedly enhances activity, indicating that eIF2B is required for full activity of mammalian eIF2B.

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Published date: 1 July 2001

Identifiers

Local EPrints ID: 56324
URI: http://eprints.soton.ac.uk/id/eprint/56324
ISSN: 0021-9258
PURE UUID: de1e4889-ac48-40a2-aa0a-d936fe9f383d

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Date deposited: 07 Aug 2008
Last modified: 15 Mar 2024 11:01

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Contributors

Author: D.D. Williams
Author: N.T. Price
Author: A.J. Loughlin
Author: C.G. Proud

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