ARCHAEAL ELONGATION-FACTOR 1-BETA IS A DIMER - PRIMARY STRUCTURE, MOLECULAR AND BIOCHEMICAL-PROPERTIES

The elongation factor 1 beta (EF-1 beta), that in eukarya and archaea promotes the replacement of GDP by GTP on the elongation factor 1 alph a . GDP complex, was purified to homogeneity from the thermoacidophili c archaeon Sulfolobus solfataricus (SsEF-1 beta). Its primary structur e was established by sequenced Edman degradation of the entire protein or its proteolytic peptides. The molecular weight of SsEF-1 beta was estimated as about 10000 or 20000 under denaturing or native condition s respectively; this finding suggests that the native protein exists a s a dimer. The peptide chain of SsEF-1 beta is much shorter than that of its eukaryotic analogues and homology is found only at their C-term inal region; no homology exists between SsEF-1 beta and eubacterial EF -Ts. Ar 50 degrees C, at a concentration of SsEF-1 beta 5-fold higher than that of SsEF-1 alpha .[H-3]GDP the rate of the exchange of [H-3]G DP for GTP becomes about 160-fold faster. An analysis of the values of the energetic parameters indicates that in the presence of SsEF-1 bet a the GDP/GTP exchange is entropically favoured. At 100 degrees C the half-life of SsEF-1 beta is about 4h.