APPENDIX IV Characteristics of Aminoacyl-tRNA Synthetases

Abstract

Table 1 gives molecular weights and subunit compositions, and information on amino acid compositions and binding sites, of aminoacyl-tRNA synthetases. Only enzymes that have been highly purified are included in the table. Some of the molecular weights may be adjusted upward in the future because proteolysis during isolation can occur. The table shows that synthetases have several subunit types. These subunit types (α, α₂, α₂β₂, α₄) represent the predominant aggregation states of the enzymes as isolated in vitro and it is conceivable that, in some cases, further studies will suggest alternate aggregation states (with full activity) can also exist. (Reprinted, with permission, from Schimmel, P. R. and D. Söll. 1979. Annu. Rev. Biochem. 48:601.)

Table 2 summarizes current information on aminoacyl-tRNA synthetase mutants. (Reprinted, with permission, from Schimmel, P. R. and D. Söll. 1979. Annu. Rev. Biochem. 48:601.)

Table
Table 1Molecular weight, quaternary structure, and substrate binding sites of highly purified aminoacyl-tRNA synthetases

Structural parametersBinding sitesSynthetaseSourcem.w.subunitstypeAA comp.^atypeno.^bAlanyl-yeast128,000 (1)none (1)αunknownArginyl-Bacillus stearothermophilus78,000 (2)none (2)αunknownamino acid1 (2)ATP1 (2)aminoacyl adenylatenone (2)Escherichia coli63,000 (3)none (3, 4)αknown (5)74,000 (4, 5)Neurospora crassa85,000 (6)none (6)αunknownAspartyl-yeast106,000 (7)none (7)αunknownCysteinyl-yeast160,000 (8)unknownrat liver240,000 (9)2 (9)α₂unknownaminoacyl adenylate2(9)Glutaminyl-E. coli69,000 (10)none (10)αknown (10)Glutamyl-