Nucleic Acids Research, 1977, Vol. 4, No. 11 3803-3820
© 1977
Articles |
Characterization of a unique enzyme complex composed of S-adenosyl-L-methionine-tRNA-methyltransferase and aminoacyl-tRNA synthetase activities
Division of Biological Sciences, University of Missouri Columbia, MO 65201, USA +Experimental Station Chemical Laboratories, University of Missouri Columbia, MO 65201, USA
Received August 1, 1977. S-adenosyl-L-methionine-tRNA methyltransferases of a murine leukemia cell line were found to exist in a high molecular weight enzyme complex. Aminoacyl-tRNA synthetase activity always co-chromatographed and co-sedi-mented with methyltransferase activity in evidence of a unique association of these two groups of enzymes. Molecular weight studies showed a probable molecular weight of 9 x 105 daltons for the intact complex which dissociates to complexes of 6 x 105 and 3 x 105 daltons. The complexes contain discrete polypeptides of 25,000–90,000 daltons as determined from SDS-gel electrophoresis. High resolution fatty acid analysis showed that only very small amounts of saponifiable lipids were associated with the purified enzyme complex. Similarly very little protein-bound sugar was found within the complex indicating that neither lipids nor sugars were involved in the protein-protein interactions of the complex. Analysis of tRNA methylated in vitro indicated the presence of most methyltransferase activities in the purified complex. Of note was the absence from the complex of the methyltransferase responsible for the production of ribo Tp.