Open AccessStudies on the Specificity of the Enzymic Synthesis of Polyribonucleotides
Author(s) -
Farber F. E.,
Chargaff E.
Publication year - 1967
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1967.tb00156.x
Subject(s) - polynucleotide phosphorylase , polynucleotide , enzyme , ribonuclease , biochemistry , bacillus cereus , dna , oligonucleotide , nucleotide , nucleic acid , chemistry , cereus , biology , microbiology and biotechnology , rna , genetics , purine nucleoside phosphorylase , gene , bacteria , purine
The purpose of this study was to ascertain whether enzymes having the same function (in this case, polynucleotide phosphorylase), but isolated from two very distant cell types, differed in their synthetic capacities. The enzymes were isolated from B. cereus , an organism possessing a DNA of a marked AT‐type (dissymmetry ratio of 1.70), and from M. lysodeikticus , whose DNA is of a pronounced GC‐type (dissymmetry ratio, 0.39). The approximate molecular weight of the B. cereus enzyme was found to be 210,000. In both instances, and with several independent enzyme preparations from either source, the mixed polynucleotides synthesized from CDP and ADP as the precursors were investigated. Three conditions of the proportions of the precursor pool were imposed, with the input ratio of CDP/ADP as 2, 1 or 0.5. Several criteria were employed for the study and the comparison of the synthetic polymers. The analysis of the base composition showed that, under equal conditions, the M. lysodeikticus enzyme incorporated a considerably higher proportion of CDP into the polynucleotides than did the B. cereus enzyme. The existence of concrete differences between polynucleotides synthesized by the two enzymes was emphasized by the study of the distribution of oligonucleotide fragments produced by the action of ribonuclease. The statistical treatment of the frequency of adenylic acid runs of different length in the various polymers demonstrated that both enzymes produced heteropolymers composed of randomly arranged nucleotide sequences. It is suggested that polynucleotide phosphorylase is species‐specific with respect to discrimination between precursors, but unspecific in its mode of action: the incorporated nucleotides are aligned in a random arrangement.