title: Studies with a homogeneous enzyme from rabbit erythrocytes catalyzing the insertion of guanine into tRNA.
abstract: 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.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D004912:Erythrocytes / Q000378:metabolism*; D006147:Guanine / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D012343:RNA, Transfer / Q000378:metabolism*; D011817:Rabbits; D014166:Transferases / Q000097:blood* / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D006147:Guanine; D012343:RNA, Transfer; D014166:Transferases