A versatile method for the coupling of protein to DNA: synthesls of αγ Marcroglobulin-Dna conjugates

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Abstract
We describe a simple, general method to link proteins covalently to ONA. The method uses two reagents, N-acetyl-N'-(p-glyoxylylbenzoyl)cystam1ne and 2-1m1noth1olane. The former reacts specifically with nonpaired quanine residues and upon reduction generates a free sulfhydryl group. The latter reacts with a protein to provide another sulfhydryl group which 1s subsequently conjugated to DNA by an intermolecular disulfide Interchange reaction. Using this method α2- macroglobulin was conjugated to plasmid DNA encoding the Herpes simplex virus-1 thymidine kinase gene or a DNA fragment containing the E.coli chlor-amphenicol acetyltransferase gene. Up to 20% of the total DNA was conjugated to α2-macroglobul1n and the α2-macroglobulin-DNA conjugate had a prote1n/DNA molar ratio of approximately two. The whole reaction takes place under very mild conditions 1n aqueous solution. The structure of DNA appears not to be significantly affected by the chemical modification. This method may prove useful In ligand directed gene transfer studies.