The Primary Structure of Transfer RNA, 1973

The study of the primary structure of nucleic acids, i. e. , the determination of the nucleotide sequence in ribosomal, transfer, and messenger types of RNA and in DNA, is an essential preliminary to the attempt to correlate the structures of these compounds with their functions. This is one of the most urgent problems in molecular biology, for until it is solved it is im­ possible to understand fully the mechanisms of fundamental living processes. Research has naturally tended to concentrate on the nucleic acids of smallest molecular weight, namely the transfer RNAs, and tremendous progress has been made in recent years in the unraveling of their structure. In 1958-1959, when structural investigation was still in its infancy, it was even doubted whether the structure of any transfer RNA could be deter­ mined. No methods of isolating homogeneous preparations were available, and it was uncertain whether the very slight physical and chemical differences between tRNAs of different specificity would be sufficient to allow successful fractionation. When the first enriched preparations were obtained, there arose the problem of whether it was possible to determine the nucleotide sequence having regard to the limited number of heterogeneous structural elements present in tRNA. These doubts were resolved in 1965, when the structure of the first nucleic acid, alanine-specific transfer RNA, was unraveled in Holley's laboratory.

Abbreviations.- 1 Transfer RNAs as Objects of Structural Research.- 2 Methods of Studying the Primary Structure of Transfer RNA.- Methods of Isolating Specimens of Individual RNAs.- Terminal Analysis.- The Stepwise-Degradation Method.- The Unit Method.- The Use of Chemical Modifications.- Fractionation of Oligonucleotides.- Spectrophotometry of Oligonucleotides.- Analysis of Oligonucleotides.- 3 The Primary Structure of Individual Transfer RNAs.- The Development of Research into the Primary Structure of tRNA Alanine tRNA from Bakers’ Yeast.- Serine tRNA from Brewers’ Yeast.- Tyrosine tRNA from Bakers’ Yeast.- Phenylalanine tRNA from Bakers’ Yeast.- Valine tRNA from Bakers’ Yeast.- Subsequent Development of Structural Research.- The Primary Structure of Individual tRNAs.- Alanine tRNA from Bakers’ Yeast.- Serine tRNA from Brewers’ Yeast.- Tyrosine tRNA from Bakers’ Yeast.- Phenylalanine tRNA from Bakers’ Yeast.- Valine tRNA from Bakers’ Yeast.- Tyrosine tRNA from E. coli.- AT-Formylmethionine tRNA from E. coli.- Methionine tRNA from E. coli.- Valine tRNA from E. coli.- Phenylalanine tRNA from E. coli.- Valine tRNA from T. utilis.- Isoleucine tRNA from T. utilis.- Tyrosine tRNA from T. utilis.- Serine tRNA from Rat Liver.- Phenylalanine tRNA from Wheat Germ.- Aspartate tRNA from Brewers’ Yeast.- Tryptophan tRNA from E. coli.- Leucine tRNA from E. coli B.- “Denaturable” Leucine tRNA from Bakers’ Yeast.- Valine tRNA2 from E. coli.- Glutamine tRNAi and tRNAn from E. coli.- Glycine tRNA from E. coli.- Common Features and Differences in Structure of Individual tRNAs.- Structure of the Isoacceptor tRNAs.- Species Differences between Individual RNAs.- 4 Minor Components of tRNA.- The Origin of the Minor Components.- The Role of the Minor Components.- Adenosine Derivatives.- Inosine.- Derivatives of Guanosine.- Uridine Derivatives.- Pseudouridine.- Dihydrouridine.- Other Uridine Derivatives.- Cytidine Derivatives.- Thiopyrimidines.- 2’-O-Methylribosides.- Unidentified Minor Components.- Conclusion.