Crosslinking of nucleic acids and proteins by bisulfite.

Sodium bisulfite is a food and beverage additive. It is also a salt of the urban air pollutant, sulfur dioxide. Bisulfite catalyzes, at neutral pH and physiological temperatures, the transamination reactions of cytosine derivatives with amines. The products of the reactions are N4-substituted cytosines. Both the alpha and epsilon-amino groups of L-lysine react with cytosine, and its nucleosides, in the presence of bisulfite. Bisulfite catalyzes the binding of cytosine to polylysine, lysine to polycytidylic acid, and polysine to polycytidylic acid. Polylysine crosslinks with heat-denatured, but not native, calf thymus DNA, in the presence of bisulfite. Other workers have demonstrated crosslinking of viral RNA with maturation and coat protein, after treatment of bacteriophage MS2 with bisulfite. Nucleic acid-protein crosslinking reactions may contribute to the adverse effects of sulfur dioxide and bisulfite upon health.