Structural organization of high-Mr mammalian aminoacyl-tRNA synthetases. Comparison of multi-enzyme complexes from different sources.

Many mammalian aminoacyl-tRNA synthetases have been isolated as high-Mr multi-enzyme complexes. These complexes often contain variable contents of synthetase activities. The complexes may also contain molecules other than synthetases such as tRNA. The observed variations in size, polypeptide composition, and content of enzyme activities of the high-Mr synthetase complexes have been sources of confusion in the understanding of the structural organization of these complexes. A unified scheme of structural organization which encompasses most observations on high-Mr complexes reported in the literature is presented.