期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：9
页码：3800-3804
DOI：10.1073/pnas.74.9.3800
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Strands of DNA that have been broken by the DNA untwisting enzyme exhibit a reduced buoyant density in alkaline CsCl due to bound protein. A covalent linkage between the DNA and the enzyme was indicated by the stability of the complex in alkali (pH greaterthan 12.7), in 7 M guanidine-HCl, and at 90 degrees in 1% Sarkosyl for 5 min. The single-strand breaks generated by the enzyme are resistant to exonuclease III, indicating that the protein is attached to one of the ends of the broken strands. The free end of the broken strand bears a 5'-hydroxyl group, indicating attachment of the protein to the 3'-phosphoryl terminus. A nucleotide-peptide linkage involving a phosphoamide bond is unlikely since the complex is resistant to 3.5 M hydroxylamine at pH 4.75.
