Interaction of wheat germ translation initiation factor 2 with GDP and GTP.
The wheat germ translation initiation factor 2 (WGeIF-2) was isolated in 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 (alpha), 40,000 (beta), 42,000 (gamma) and 52,000 (delta). The beta- and gamma-subunits (but not the alpha-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 GTP were measured. In our evaluation the WGeIF-2 affinity for GDP (KdGDP = 1.5 x 10(-7) M) was only 10 times higher than for GTP (KdGTP = 1.5 x 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.
Shaikhin
S M
SM
Ajtkhozhin Institute of Molecular Biology and Biochemistry, Kazakh Academy of Sciences, Alma-Ata, Michurina, Kazakhstan.
Smailov
S K
SK
Lee
A V
AV
Kozhanov
E V
EV
Iskakov
B K
BK
D000818:Animals; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D008970:Molecular Weight; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011817:Rabbits; D014908:Triticum
D015852:Eukaryotic Initiation Factor-2; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate