Chemical modification of the recombinant human alpha A- and beta-interferons

Chemical modification has been used to map the residues essential for the antiviral activity of the recombinant human alpha A- and beta-interferons. Modification of His residues with diethylpyrocarbonate and N alpha-tosyl-L-lysyl chloromethylketone does not inhibit both interferons, whereas N alpha-tosyl-L-phenylalanyl chloromethylketone significantly suppressing the activity of beta-interferon does not affect the activity of alpha A-interferon. After the modification of 1, 2 and 3 Lys residues from 11 ones with 3-(2-pyridyldithio)propionic acid N-hydroxy-succinimide ester alpha A-interferon reveals 100%, 50% and 10% of the initial activity, respectively. Modification of Trp residues with H2O2, 2-nitrobenzenesulfenyl chloride or 2-hydroxy-5-nitrobenzylbromide inactivates alpha A- and beta-interferons completely. Presumably Trp residue(s) is essential for the antiviral activity of alpha- and beta-interferons.