Bovine tryptophanyl-tRNA synthetase is able to form a complex with glyceraldehyde-3-phosphate dehydrogenase. The complex formation (i) does not influence the tryptophan-dependent PPi-ATP exchange reaction and (ii) involves predominantly the N-terminal dispensable domain of the synthetase. Glyceraldehyde-3-phosphate dehydrogenase was shown to be capable of interacting simultaneously with tryptophanyl-tRNA synthetase and with ribosomal RNA to form a ternary complex. It is proposed that compartmentation of some aminoacyl-tRNA synthetases in certain cases might be achieved via 'adapter' molecules which can bind at once to ribonucleic acids and to aminoacyl-tRNA synthetases.