The conversion of eIF-2.GDP to eIF-2.GTP by eIF-2B requires Met-tRNA(fMet)

Biochem Biophys Res Commun. 1991 Dec 31;181(3):1500-7. doi: 10.1016/0006-291x(91)92109-w.


We have investigated why the recycling of eIF-2.GDP to eIF-2.GTP, mediated by the guanine nucleotide exchange factor eIF-2B, is rapid in rabbit reticulocyte lysate, reconstituted for optimal protein synthesis, but slow in an isolated reaction with purified eIF-2B. We have found that purified eIF-2B dissociates eIF-2.[3H]GDP as efficiently in the presence of GTP as it does in the presence of GDP provided Met-tRNA(fMet) is added. tRNA(fMet) is ineffective, and there is no Met-tRNA(fMet) requirement for exchange with GDP. Exchange of eIF-2 bound GDP for GTP is completely dependent upon Met-tRNA(fMet) in the presence of ATP, suggesting that under physiological conditions efficient recycling of eIF-2.GDP to eIF-2.GTP requires conversion of the latter, a relatively unstable complex, to a more stable Met-tRNA(fMet).eIF-2.GTP complex.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding, Competitive
  • Cell-Free System
  • Eukaryotic Initiation Factor-2 / metabolism*
  • Guanine Nucleotide Exchange Factors
  • Guanosine Diphosphate / metabolism*
  • Guanosine Triphosphate / metabolism*
  • Guanylyl Imidodiphosphate / metabolism
  • Kinetics
  • Nucleotides / metabolism
  • Nucleotides / pharmacology
  • Proteins / metabolism*
  • RNA, Transfer, Amino Acyl / metabolism
  • RNA, Transfer, Met / metabolism*
  • Rabbits
  • Reticulocytes / metabolism


  • Eukaryotic Initiation Factor-2
  • Guanine Nucleotide Exchange Factors
  • Met-tRNA(f)(Met)
  • Nucleotides
  • Proteins
  • RNA, Transfer, Amino Acyl
  • RNA, Transfer, Met
  • tRNA, formylmethionine-
  • Guanosine Diphosphate
  • Guanylyl Imidodiphosphate
  • Guanosine Triphosphate