Enzymes of Nucleic Acid Metabolism from Mung Bean Sprouts
III. THE IDENTIFICATION OF 5'-MONONUCLEOTIDES AS HYDROLYSIS PRODUCTS OF RIBONUCLEASE M2
Tom L. Walters 1 and Hubert S. Loring 1
From the
1 From the Department of Chemistry, Stanford University, Stanford, California 94305
The products of ribonuclease M2 action on tobacco mosaic virus ribonucleic acid in the absence and presence of added Zn++ were fractionated by chromatography on diethylaminoethyl cellulose and shown to consist of mixtures of mononucleotides, dinucleotides, higher oligonucleotides, and minor amounts of nucleosides. In the absence of added Zn++, the degradation of the RNA was relatively incomplete, with 27% of the total absorbance appearing in the mononucleotide fraction and a majority as di- and higher oligonucleotides. With added Zn++, 60% of the absorbance appeared in the mononucleotide fraction, 25% as dinucleotides, and 11% as higher oligonucleotides.
The mononucleotide components both without and with added Zn++ were fractionated and identified as 5'-mononucleotides. Without added Zn++, about 60 mole % of the mononucleotide fraction was recovered as adenosine 5'-monophosphate and about 20 mole % each as uridine 5'-monophosphate and guanosine 5'-monophosphate, with no definite recovery of cytidine 5'-monophosphate (roughly two-thirds of the adenosine residues and about one-sixth each of the uridine and guanosine of tobacco mosaic virus RNA). With added Zn++, all of the adenosine residues were recovered as 5'-AMP (and adenosine); about one-half of the uridine and guanosine, respectively, as 5'-UMP and 5'-GMP; and about one-fifth of the cytidine, as CMP.
The significance of these results in relation to the specificity of RNase M2 action, to the possible Zn++ metalloprotein nature of RNase M2, and to tobacco mosaic virus RNA structure is discussed.
Submitted on December 8, 1965
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