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：1980
卷号：77
期号：8
页码：4574-4577
DOI：10.1073/pnas.77.8.4574
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Spin-labeled copolymers of 4-thiouridine and uridine (ls4U,U)n] that contain various amounts of spin label (l) were synthesized by either (i) chemical alkylation of the 4-thiouridine-uridine copolymers (s4U,U)n prepared by copolymerizing 4-thiouridine 5'-diphosphate (s4UDP) and UDP or (ii) copolymerization of spin-labeled s4UDP with UDP using polynucleotide phosphorylase. The effect of (s4U,U)n and (ls4U,U)n on avian myeloblastosis virus (AMV) RNA-dependent DNA polymerase (RNA-dependent DNA nucleotidyltransferase, EC 2.7.7.7 ; reverse transcriptase) was studied to determine whether the presence of potentially reactive thiol groups or spin labels enhances the inhibitory properties of the copolymers as compared to (U)n. Inhibition by (s4U,U)n gradually increases as the percentage of thiolation increases. Enhanced inhibition by (s4U,U)n appears to be due to the interaction of the thiol groups of (s4U,U)n with the thiol group(s) of the polymerase, because inhibition by (s4U,U)n (8% thiolated) in the presence of dithiotreitol resembles that by (U)n. In contrast, inhibition by (ls4U,U)n containing 3% spin label resembles that by (U)n; however, increasing the spin label to 6% or 12% results in enhanced inhibition by (ls4U,U)n as compared to that by (U)n, and dithiothreitol has no effect on enhanced inhibition by (ls4U,U)n. These results suggest that the mechanism of inhibition observed with (ls4U,U)n with a ls4U:U ratio > 1:33 differs from the mechanism for (s4U,U)n and involves complex formation between the spin label and the essential Zn2+ of RNA-dependent DNA polymerase.
