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 coupling to the cognate tRNA, The enzyme is made of two domains: an N-terminal catalytic domain and a C-terminal domain that is necessary for tRNA binding and for which it was not possible to determine the structure by X-ray crystallography. We determined the secondary structure of the C-terminal domain of the tyrosyl-tRNA synthetase from Bacillus stearothermophilus by nuclear magnetic resonance methods and found that it is of the alpha+beta type, Its arrangement differs from those of the other anticodon binding domains whose 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 flexible linker between the two domains. (C) 1999 Federation of European Biochemical Societies.