The interaction between the archaeal elongation factor 1alpha and its nucleotide exchange factor 1beta

In Sulfolobus solfataricus the binding of the exchange factor 1b (SsEF-1b) to SsEF-1aGDP displaces the nucleotide and the SsEF-1aSsEF-1b complex is formed. The complex itself is stable, but it dissociates upon the addition of GDP or Gpp(NH)p but not ATP. Since the rate of the formation of the SsEF-1aSsEF-1b complex is significatively slower than the rate of the nucleotide exchange catalyzed by SsEF-1b it can be inferred that in vivo the GDP/GTP exchange reaction proceeds via an SsEF-1aSsEF-1b interaction without involving the formation of a stable binary complex as an intermediate.