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Interaction of wheat germ translation initiation factor 2 with GDP and GTP

Authors
Journal
Biochimie
0300-9084
Publisher
Elsevier
Publication Date
Volume
74
Issue
5
Identifiers
DOI: 10.1016/0300-9084(92)90085-s
Keywords
  • Wheat Germ Eif-2
  • Gdp And Gtp Binding
  • Translation Regulation In Plants

Abstract

Abstract The wheat germ translation initiation factor 2 (WGeIF-2) was isolated a homogeneous state by an efficient procedure and characterized. Its molecular mass, as determined by a gel-filtration method is approximately 150 000 Da. According to SDS-PAGE WGeIF-2 consists of four subunits with M r 37 000 (α), 40 000 β), 42 000 (γ) and 52 000 (δ). The β- and γ-subunits (but not the α-subunit) of WGeIF-2 can be readily phosphorylated by the double-stranded RNA activated kinase isolated from rabbit reticulocytes. Dissociation constants for WGeIF-2 complexes with GDP and GPT were measured. In our evaluation the WGeIF-2 affinity for GDP ( K dGDP = 1.5 × 10 −7 M) was only 10 times higher than for GTP ( K dGTP = 1.5 × 10 −6 M), while for rabbit reticulocyte eIF-2 (RReIF-2) the difference has been estimated as as much as two orders of magnitude in accordance with the literature. Close values of dissociation constants for WGeIF-2 complexes with guanine nucleotides suggest that at a sufficiently high [GTP]/[GDP] ratio the nucleotide exchange in wheat cells may take place without the participation of specific factor (eIF-2B) which catalyzes the nucleotide exchange on eIF-2 from mammalian cells.

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