STRUCTURE AND IMPORTANCE OF THE DIMERIZATION DOMAIN IN ELONGATION FACTOR TS FROM THERMOS THERMOPHILUS. Youxing Jiang^*, Steffen Nock⁺, Martina Nesper⁺, Mathias Sprinzl⁺, Paul B. Sigler^{#[[daggerdbl]]}, ^*The Department of Chemistry, ^#The Department of Molecular Biophysics and Biochemistry and the Howard Hughes Medical Institute, Yale Univ., CT 06511, USA, ⁺Laboratorium fur Biochemie, Universitat Bayreuth, ^{[[daggerdbl]]}To whom correspondence should be addressed

Elongation factor Ts (EF-Ts) functions as a nucleotide exchange factor which catalyze the GDP/GTP exchange in elongation factor Tu. Thermus thermophilus elongation factor Ts forms a homodimer in solution. The crystal structure of the EF-Ts dimerization domain has been solved and refined to a resolution of 1.7 Å. This high resolution structure gives a clear picture of the dimerization interactions of EF-Ts. The three-stranded anti-parallel [[beta]]-sheet of each subunit comes together to form a [[beta]]-sandwich held together by a disulfide bond between the Cysl90 of each subunit and by the hydrophobic core constructed by Ile60, His62, Ile64, Gly71, Leu73 and Phel92. Based on the structure, two mutants, C19OA and L73D, were designed to disrupt the dimer interface. The activity analyses show that monomeric EF-Ts loses the ability to catalyze exchange of GDP/GTP in EF-Tu which indicates that Thermus thermophilus EF-Ts functions as a homodimer.