Noncovalent Binding of 4-Nitroquinoline-N-Oxide to Proteins

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Binding of 4NQO to various kinds of enzymes or proteins was studied. Each one of proteins was mixed with 4NQO in 0.4 mM NaHCO_3 solution and eluted through Ultrogel ACA 22 column. Radioactivity of ^<14>C-labeled 4NQO found in protein fraction was measured. 4NQO bound hardly to polyglutamic acid and polyaspertic acid, somewhat to serum albumin, insulin, trypsin, RNA polymerase and DNA polymerase, and markedly to urease which is an SH enzyme. Lactate dehydrogenase, one of SH enzymes, aggregated with 4NQO. The binding of SH enzyme with the N-oxide would be attributable to a noncovalent binding such as [chemical formula], because 4NQO-urease binding yield markedly decreased in the presence of sodium dodecyl sulfate or cysteine, and also 4NQO-bound urease released 4NQO by the addition of sodium dodecyl sulfate. Sklobovskaya and Ryabchenko and Strazhevskaya et al. have been studied the DNA-protein crosslinking induced by ionizing radiation at low doses. The latter workers suggested the participation of acidic protein in the crosslinking. This type of crosslink, however, was not observed under conditions such as the presence of sodium dodecyl sulface (SDS), the low pH, or the high salt concentration. It indicates that such crosslink is due to noncovalent binding of the specific amino acid residues of protein to the radiation-modified portion in DNA molecule. Rhaese has identified adenine-7-N-oxide as one of radiolytic products of adenine.
日本放射線影響学会の論文

Noncovalent Binding of 4-Nitroquinoline-N-Oxide to Proteins

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