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A study of some molecular and kinetic properties of two tRNA methyltransferases from mouse plasmocytoma
Abstract:
A tRNA(adenine-1)methyltransferase and a tRNA(cytosine-5)methyltransferase have been partially purified from mouse plasmocytoma MOPC 173. Their apparent Mr are 200000-230000 and 110000-140000, respectively, as determined by gel filtration and density gradient centrifugation. Both enzymes exhibit maximum activity in the presence of high concentrations of monovalent cations (0.175 M and 0.25 M KCl, respectively) and in the absence of magnesium. Their kinetic constants have been determined at various KCl concentrations, with several tRNA species as substrates. These constants may differ by more than one order of magnitude, depending upon the substrate used, and they are strongly dependent upon the ionic concentration as well. The possibility that the tRNA(adenine-1)methyltransferase from mouse plasmocytoma is different from the homologous enzyme purified from a normal rat tissue [Glick, J. M. and Leboy, P. S. (1977) J. Biol. Chem. 252, 4790-4795] is discussed.
Insights
Researchers purified two key tRNA methyltransferases from mouse plasmocytoma cells. Enzyme activity and kinetics were analyzed, revealing dependence on substrate and ionic concentration.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Transfer RNA (tRNA) modifications are crucial for protein synthesis.
- Methylation of tRNA bases plays a significant role in tRNA structure and function.
- Understanding tRNA methyltransferases is vital for comprehending gene expression regulation.
Purpose of the Study:
- To partially purify and characterize two specific tRNA methyltransferases from mouse plasmocytoma MOPC 173.
- To investigate the enzymatic properties, including molecular weight, optimal conditions, and kinetic parameters, of these enzymes.
- To compare the purified tRNA(adenine-1)methyltransferase with its counterpart from normal rat tissue.
Main Methods:
- Partial purification of tRNA(adenine-1)methyltransferase and tRNA(cytosine-5)methyltransferase using biochemical techniques.
- Determination of apparent molecular weight (Mr) via gel filtration and density gradient centrifugation.
- Enzyme kinetic analysis, including determination of kinetic constants with various tRNA substrates at different KCl concentrations.
Main Results:
- Two distinct tRNA methyltransferases were purified, with apparent Mr of 200,000–230,000 and 110,000–140,000.
- Both enzymes showed optimal activity at high monovalent cation concentrations (0.175 M and 0.25 M KCl, respectively) and without magnesium.
- Kinetic constants varied significantly with different tRNA substrates and were highly dependent on ionic concentration.
Conclusions:
- The characterized tRNA methyltransferases possess distinct properties influenced by substrate and ionic strength.
- The findings provide insights into the regulation and substrate specificity of tRNA methylation.
- Further investigation is warranted to elucidate the potential differences between the mouse plasmocytoma tRNA(adenine-1)methyltransferase and the homologous enzyme from normal rat tissue.