32. the nucleic acids of microorganisms 159 



2. Ribonucleic Acid 



a. Sugar 



Long ago it was shown that D-ribose was the sugar constituent of the 

 UNA of yeast. 110 During recent years, D-ribose was identified in different 

 UNA 79 ' UI including that of microorganisms M. tuberculosis avium,™ Clostrid- 

 ium perfringens, 112 E. coli, m and Euglena gracilis. 1 ^ It was shown in the 

 RNA of yeast 115 as well. The principal pentose constituent of the nucleotides 

 of all ribonucleic acids, regardless of their origin, seems to be D-ribose. It 

 is not ruled out, however, that some other minor sugar constituents can 

 be present in certain cases. 114 • I15a 



b. Nitrogenous Constituents 



Until recently, only the usual bases, guanine, adenine, cytosine, and 

 uracil, were known as RXA constituents. The first communications on the 

 discovery of a fifth nucleotide in alkaline hydrolyzates of yeast RNA ap- 

 peared simultaneously from two laboratories in 1957. 116, m This new nu- 

 cleotide yielded, on degradation, a new nucleoside which was shown to be 

 a derivative of uracil. It is most likely that this compound represents 

 5-ribosyluracil. 118 - 119 The designation "pseudouridine" has been proposed 

 for the nucleoside. 119 The isolation of both the 2'- and 3'-phosphates of this 

 nucleoside by alkaline hydrolysis shows it to be a regular constituent of 

 the RXA chain. In addition to yeast RNA, a substance with the properties 

 of the new nucleotide was demonstrated in alkaline hydrolyzates of bacterial 

 RNA, from A. aerogenes and B. cereus, 93 in the RNA of a flagellate, E. 

 gracilis, Ui as well as in higher forms. 93 



That the list of RNA constituents is not restricted to the four common 

 bases and may turn out to be much more complicated owing to the presence 

 of various "minor constituents" was confirmed, in addition to the data 

 mentioned above, by several new findings published in 1958. This group 

 of data deals with the isolation of a whole set of methylated purines and 



110 P. A. Levene and W. A. Jacobs, Ber. 42, 2102, 2469, 2474, 2703 (1909). 



111 B. Magasanik, in "The Nucleic Acids" (E. Chargaff and J. N. Davidson, eds.), 

 Vol. 1, p. 373. Academic Press, New York, 1955. 



112 C. H. Parsons, Arch. Biochem. Biophys. 47, 76 (1953). 



113 A. Lombard and E. Chargaff, Biochim. et Biophys. Acta 25, 549 (1957). 



114 G. Bravverman and E. Chargaff, Biochim. et Biophys. Acta 31, 172 (1959). 



115 E. Vischer and E. Chargaff, J. Biol. Chem. 176, 715 (1948). 



" 5a J. D. Smith and D. B. Dunn, Biochim. et Biophys. Acta 31, 573 (1959). 



116 F. F. Davis and F. W. Allen, J. Biol. Chem. 227, 907 (1957). 



117 W. E. Cohn, Federation Proc 16, 166 (1957). 



118 C. Yu and F. W. Allen, Biochim. et Biophys. Acta 32, 393 (1959). 



119 W. E. Cohn, Biochim. el Biophys. Acta 32, 569 (1959). 



