Studies with a homogeneous enzyme from rabbit erythrocytes catalyzing the insertion of guanine into tRNA

J Biol Chem. 1978 Dec 25;253(24):9082-7.


An enzyme that catalyzes a post-transcriptional modification of tRNA, resulting in replacement of a base from tRNA by guanine, has been purified 2600-fold from rabbit erythrocyte cytosol. The purest preparation migrates as a single protein band on polycrylamide gel electrophoresis and the enzymatic activity co-electrophoreses with this protein. The native enzyme has a molecular weight of 104,000 and is dissociated into two subunits of Mr= 60,000 and 43,000. The Km for guanine is 1.5 x 10(-7) M and for a pure guanine-accepting tRNA is 3.3 x 10(-9) M. The amino acid composition of the pure enzyme has been determined. To our knowledge this is the first study in which the molecular characteristics of a pure enzyme capable of modifying an internal position in tRNA has been reported.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acids / analysis
  • Animals
  • Erythrocytes / metabolism*
  • Guanine / metabolism*
  • Kinetics
  • Molecular Weight
  • RNA, Transfer / metabolism*
  • Rabbits
  • Transferases / blood*
  • Transferases / isolation & purification


  • Amino Acids
  • Guanine
  • RNA, Transfer
  • Transferases