Secondary structure of the C-terminal domain of the tyrosyl-transfer RNA synthetase from Bacillus stearothermophilus: a novel type of anticodon binding domain?

The tyrosyl-tRNA synthetase catalyzes the activation of tyrosine and its co upling to the cognate tRNA, The enzyme is made of two domains: an N-termina l catalytic domain and a C-terminal domain that is necessary for tRNA bindi ng and for which it was not possible to determine the structure by X-ray cr ystallography. We determined the secondary structure of the C-terminal doma in of the tyrosyl-tRNA synthetase from Bacillus stearothermophilus by nucle ar magnetic resonance methods and found that it is of the alpha+beta type, Its arrangement differs from those of the other anticodon binding domains w hose structure is known. We also found that the isolated C-terminal domain behaves as a folded globular protein, and we suggest the presence of a flex ible linker between the two domains. (C) 1999 Federation of European Bioche mical Societies.