Disordered C-terminal domain of tyrosyl-tRNA synthetase: Secondary structure prediction

The C-terminal domain (residues 320-419) of tyrosyl-tRNA synthetase (TyrRS) from Bacillus stearothermophilus is disordered in the crystal structure an d involved in the binding of the anticodon arm of tRNA(Tyr). The sequences of 11 TyrRSs of prokaryotic or mitochondrial origins were aligned and the a lignment showed the existence of conserved residues in the sequences of the C-terminal domains. A consensus could be deduced from the application of f ive programs of secondary structure prediction to the 11 sequences of the q uery set. These results suggested that the sequences of the C-terminal doma ins determined a precise and conserved secondary structure. They predicted that the C-terminal domain would have a mixed fold (alpha/beta or alpha+bet a), with the alpha-helices in the first half of the sequence and the beta-s trands mainly in its second half. Several programs of fold recognition from sequence alone, by threading onto known structures, were applied but none of them identified a type of fold that would be common to the different seq uences of the query set. Therefore, the fold of the C-terminal, anticodon b inding domain might be novel. (C) Societe francaise de biochimie et biologi e moleculaire / Elsevier, Paris.