[Role of the anticodon loop in triggering conformational changes of tryptophanyl-tRNA synthetase by tRNA Trp]

The circular dichroic spectrum of the bovine tRNATrp is altered in complex with homologous tryptophanyl-tRNA synthetase showing the conformational changes of the substrate under the action of enzyme. The conversion of the exposed cytosine into uridine bases in tRNATrp (beef, yeast) does not prevent complex formation but abolishes the tRNA action on the limited proteolysis of the synthetase. It was shown that elimination of this type of tRNA activity is solely attributed to the cytosine leads to uridine conversion in the anticodon loop. A conclusion is made that the anticodon loop of the tRNATrp plays a dominant role in triggering conformational changes of the synthetase under substrate action whereas the CCA-end is not directly involved in this process.