Cheng S, Van Houten B, Gamper H B, Sancar A, Hearst J E
Department of Chemistry, University of California, Berkeley.
J Biol Chem. 1988 Oct 15;263(29):15110-7.
A series of site-specifically cross-linked, three-stranded complexes has been prepared using the RecA protein, form I (covalently closed and negatively supercoiled) pUC19 plasmid, and eight psoralen-monoadducted oligonucleotides between 30 and 107 residues in length. Complexes formed much less efficiently if linearized pUC19 was used as the duplex substrate. Quantitative analysis indicates that although RecA is able to utilize a 30-mer in its homologous pairing reaction, incorporation at 50% efficiency requires a single-stranded substrate at least 50 residues long. These three-stranded complexes have been used to study the action mechanism for cross-link repair by ABC excinuclease, and the results are consistent with the recent model of Van Houten, B., Gamper, H., Holbrook, S. R., Hearst, J. E., and Sancar, A. (1986b) Proc. Natl. Acad. Sci. U. S. A. 83, 8077-8081.
利用RecA蛋白、I型（共价闭合且负超螺旋）pUC19质粒以及8种长度在30至107个残基之间的补骨脂素单加合物寡核苷酸，制备了一系列位点特异性交联的三链复合物。如果使用线性化的pUC19作为双链底物，复合物形成的效率要低得多。定量分析表明，尽管RecA能够在其同源配对反应中利用30聚体，但要达到50%的掺入效率，需要至少50个残基长的单链底物。这些三链复合物已被用于研究ABC核酸外切酶交联修复的作用机制，结果与Van Houten, B., Gamper, H., Holbrook, S. R., Hearst, J. E., 和Sancar, A.（1986b）发表在《美国国家科学院院刊》83, 8077 - 8081上的最新模型一致。
