Purification and characterization of the unusual deoxynucleoside, alpha-N-(9-beta-D-2'-deoxyribofuranosylpurin-6-yl)glycinamide, specified by the phage Mu modification function.

Bacteriophage Mu encodes a protein that modifies approximately equal to 15% of DNA adenine residues to a new and unusual form. Modified DNA was enzymatically digested to deoxynucleosides, and the products were fractionated by HPLC. A modified adenine nucleoside, designated dA'x, was purified and its molecular structure was established by mass spectrometry. We show that dA'x is alpha-N-(9-beta-D-2'-deoxyribofuranosylpurin-6-yl)-glycinamide. The dA'x obtained from DNA was indistinguishable from the synthetic product with respect to its chromatographic behavior (HPLC and gas chromatography) and mass spectrum. Acid hydrolysis degrades dA'x to produce N6-carboxymethyladenine; this compound corresponds to the base Ax observed in earlier studies.