Structure and importance of the dimerization domain in elongation factor Ts from Thermus thermophilus.
Elongation factor Ts (EF-Ts) functions as a nucleotide-exchange factor by binding elongation factor Tu (EF-Tu) and accelerating the GDP dissociation from EF-Tu; thus EF-Ts promotes the transition of EF-Tu from the inactive GDP form to the active GTP form. Thermus thermophilus EF-Ts exists as a stable dimer in solution which binds two molecules of EF-Tu to form a (EF-Tu.EF-Ts)2 heterotetramer. Here we report the crystal structure of the dimerization domain of EF-Ts from T. thermophilus refined to 1.7 A resolution. A three-stranded antiparallel beta-sheet from each subunit interacts to form a beta-sandwich that serves as an extensive dimer interface tethered by a disulfide bond. This interface is distinctly different from the predominantly alpha-helical one that stabilizes the EF-Ts dimer from Escherichia coli [Kawashima, T., et al. (1996) Nature 379, 511-518]. To test whether the homodimeric form of T. thermophilus EF-Ts is necessary for catalyzing nucleotide exchange, the present structure was used to design mutational changes within the dimer interface that disrupt the T. thermophilus EF-Ts dimer but not the tertiary structure of the subunits. Surprisingly, EF-Ts monomers created in this manner failed to catalyze nucleotide exchange in EF-Tu, indicating that, in vitro. T. thermophilus EF-Ts functions only as a homodimer.
Jiang
Y
Y
Department of Chemistry, Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06520, USA.
Nock
S
S
Nesper
M
M
Sprinzl
M
M
Sigler
P B
PB
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001704:Biopolymers; D002384:Catalysis; D002417:Cattle; D006153:Guanosine Diphosphate / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D010444:Peptide Elongation Factor Tu / Q000737:chemistry; D010445:Peptide Elongation Factors / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D016963:Thermus thermophilus / Q000737:chemistry* / Q000235:genetics
D001704:Biopolymers; D009838:Oligodeoxyribonucleotides; D010445:Peptide Elongation Factors; C023512:elongation factor Ts; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D010444:Peptide Elongation Factor Tu