Juodka B, Pfütz M, Werner D
Department of Biochemistry and Biophysics, Vilnius University, Lithuania.
Nucleic Acids Res. 1991 Dec 11;19(23):6391-8. doi: 10.1093/nar/19.23.6391.
DNA from Ehrlich ascites tumor (EAT) cells and from human placenta was examined for covalent bonds between hydroxy amino acid residues in peptides and nucleotide phosphate groups. The residual proteinaceous material in highly purified DNA was radiolabelled with 125Iodine and the linking-groups between peptides and nucleotides released by combined protease and nuclease treatment were investigated with respect to their chemical and enzymatic stabilities. The residual nucleotide(s)-peptide(s) fraction from DNA isolated after prolonged alkaline cell lysis and phenol extraction contains mainly alkali and acid-stable but phosphodiesterase-sensitive peptide-nucleotide complexes which indicates phosphodiesters between tyrosyl residues in peptides and nucleotide phosphates. In contrast, the linking-group fraction from DNA isolated under native conditions contains additional peptide components. (a) Phospho-peptides that co-purify with DNA but that are not covalently bound to nucleotides. (b) A fraction of peptides that is released from nucleotides by alkali in a time and concentration-dependent reaction. Evidence is presented indicating that the latter fraction involves phospho-triesters between hydroxy amino acid residues in peptides and internucleotide phosphates. The phosphodiesters between hydroxy amino acids and nucleotide phosphates representing the predominant class of peptide-nucleotide complexes in alkali-denatured DNA are most likely side products of peptide-nucleotide phospho-triester hydrolysis.
对艾氏腹水瘤（EAT）细胞和人胎盘的DNA进行了检测，以研究肽中羟基氨基酸残基与核苷酸磷酸基团之间的共价键。用125碘对高度纯化的DNA中残留的蛋白质物质进行放射性标记，并研究了蛋白酶和核酸酶联合处理释放的肽与核苷酸之间的连接基团的化学和酶稳定性。经过长时间碱性细胞裂解和苯酚提取后从DNA中分离出的残留核苷酸-肽部分主要包含对碱和酸稳定但对磷酸二酯酶敏感的肽-核苷酸复合物，这表明肽中的酪氨酰残基与核苷酸磷酸之间存在磷酸二酯键。相比之下，在天然条件下从DNA中分离出的连接基团部分包含其他肽成分。（a）与DNA共纯化但未与核苷酸共价结合的磷酸肽。（b）一部分肽在碱作用下以时间和浓度依赖性反应从核苷酸中释放出来。有证据表明，后一部分涉及肽中羟基氨基酸残基与核苷酸间磷酸之间的磷酸三酯。在碱变性DNA中，羟基氨基酸与核苷酸磷酸之间的磷酸二酯是肽-核苷酸复合物的主要类型，很可能是肽-核苷酸磷酸三酯水解的副产物。
