The primary structure of oligonucleotides. Partial apurinization as a method to determine the positions of purine and pyrimidine residues

The DNA double helix fifty years on

This year marks the 50th anniversary of the proposal of a double helical structure for DNA by James Watson and Francis Crick. The place of this proposal in the history and development of molecular biology is discussed. Several other discoveries that occurred in the middle of the twentieth century were perhaps equally important to our understanding of cellular processes; however, none of these captured the attention and imagination of the public to the same extent as the double helix. The existence of multiple forms of DNA and the uses of DNA in biological technologies is presented. DNA is also finding increasing use as a material due to its rather unusual structural and physical characteristics as well as its ready availability.

Studies of the functional topography of Escherichia coli RNA polymerase. A method for localization of the sites of affinity labelling

A method is proposed for localization of the sites of affinity labelling of the beta subunit of Escherichia coli RNA polymerase. The principle of this method is similar to that of the methods of rapid sequencing of nucleic acids. The polypeptide bearing a radioactive affinity label at one of the amino acid residues is subjected to short-term treatment with cyanogen bromide. The conditions of this reaction are selected in such a way that less than one cleavage occurs on average per polypeptide chain. Two series of radioactive peptides are formed, one involving all the possible N-terminal peptides and the other the C-terminal peptides. The distribution of the lengths of these peptides is studied by means of gel electrophoresis and compared with the theoretical ones based on the known amino acid sequence of the beta subunit. Obviously, the affinity label resides between the C-terminus of the shortest N-terminal radioactive peptide and the N-terminus of the shortest C-terminal radioactive peptide. In order to increase reliability and resolution of the method, partial trypsinolysis may be employed. The evidence obtained suggests that lysine residues over the regions 1036-1066, 1234-1242, and histidine-1237 are situated in the nearest neighbourhood to, or directly involved in the formation of the active center of initiating substrate binding of the beta subunit of E. coli RNA polymerase.

The primary structure of Escherichia coli RNA polymerase. Nucleotide sequence of the rpoB gene and amino-acid sequence of the beta-subunit

The combined structural study of proteins and of their corresponding genes utilizing the methods of both protein and nucleotide chemistry greatly accelerates and considerably simplifies both the nucleotide and protein structure determination and, in particular, enhances the reliability of the analysis. This approach has been successfully applied in the primary structure determination of the beta and beta' subunits of Escherichia coli DNA-dependent RNA polymerase and of their structural genes, yielding a continuous nucleotide sequence (4714 base pairs) that embraces the entire rpoB gene, the initial part of the rpoC gene and the intercistronic region, together with the total amino acid sequence of the beta subunit, comprising 1342 residues, and the N-terminal sequence of the beta' subunit (176 residues).

Primary structure of an EcoRI fragment of lambda imm434 DNA containing regions cI-cro of phage 434 and cII-o of phage lambda

Digestion of phage lambda imm434 DNA with restriction endonuclease EcoRI yields 7 fragments. The shortest among them (1287 bp) contains the right part of the phage 434 immunity region and the phage DNA portion proximal to it. The complete primary structure of this fragment has been determined using the chemical method of DNA sequencing. Hypothetical amino-acid sequences of proteins coded by the cro gene of phage 434 and the cII gene of phage lambda, as well as NH2-terminal amino-acid sequences of the cI protein of phage 434 and the O protein of phage lambda, have been deduced solely on the basis of the DNA sequence. The fragment studied contains also the pR and probably prm promoters and the oR operator of phage 434. The sequence coding for them differs from the respective DNA sequence of phage lambda.