Nelson J A, Levy J A, Leong J C
Proc Natl Acad Sci U S A. 1981 Mar;78(3):1670-4. doi: 10.1073/pnas.78.3.1670.
Human placental extracts contain a specific inhibitor of mammalian retroviral RNA-directed DNA polymerase (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7) activity. This inhibitor copurifies with retrovirus-like particles in human placental extracts. The inhibitor can be removed from these particles by salt extraction, which leads to the recovery of the polymerase activity. Thus, the inhibitor does not irreversibly inactivate the particle-associated RNA-directed DNA polymerase activity. The inhibitory preparation contained no nuclease, protease, or phosphatase activity. Because its inhibitory action can be eliminated by the addition of more virus to the reaction, nonspecific inactivation of enzyme substrate has been ruled out. A partial characterization of the inhibitor indicates that it is (i) insensitive to ether, trypsin, and phospholipase C; (ii) stable to heat and pH 2-12; and (iii) nondialyzable.
人胎盘提取物含有一种特异性抑制哺乳动物逆转录病毒RNA指导的DNA聚合酶（脱氧核苷三磷酸：DNA脱氧核苷酸转移酶，EC 2.7.7.7）活性的物质。这种抑制剂与人胎盘提取物中的逆转录病毒样颗粒共纯化。该抑制剂可通过盐提取从这些颗粒中去除，从而使聚合酶活性得以恢复。因此，该抑制剂不会不可逆地使颗粒相关的RNA指导的DNA聚合酶活性失活。该抑制制剂不含有核酸酶、蛋白酶或磷酸酶活性。由于加入更多病毒到反应中可消除其抑制作用，因此排除了酶底物的非特异性失活。对该抑制剂的部分特性分析表明，它（i）对乙醚、胰蛋白酶和磷脂酶C不敏感；（ii）对热和pH 2 - 12稳定；（iii）不可透析。
