Marquez Victor E, Ben-Kasus Tsipi, Barchi Joseph J, Green Karen M, Nicklaus Marc C, Agbaria Riad
Laboratory of Medicinal Chemistry, Center for Cancer Research, National Cancer Institute at Frederick, National Institutes of Health, 376 Boyles St., Frederick, MD, 21702, USA.
J Am Chem Soc. 2004 Jan 21;126(2):543-9. doi: 10.1021/ja037929e.
Two isomers of methanocarba (MC) thymidine (T), one an effective antiherpes agent with the pseudosugar moiety locked in the North (N) hemisphere of the pseudorotational cycle (1a, N-MCT) and the other an inactive isomer locked in the antipodean South (S) conformation (1b, S-MCT) were used to determine whether kinases and polymerases discriminate between their substrates on the basis of sugar conformation. A combined solid-state and solution conformational analysis of both compounds, coupled with the direct measurement of mono-, di-, and triphosphate levels in control cells, cells infected with the Herpes simplex virus, or cells transfected with the corresponding viral kinase gene (HSV-tk), suggests that kinases prefer substrates that adopt the S sugar conformation. On the other hand, the cellular DNA polymerase(s) of a murine tumor cell line transfected with HSV-tk incorporated almost exclusively the triphosphate of the locked N conformer (N-MCTTP), notwithstanding the presence of higher triphosphate levels of the S-conformer (S-MCTTP).
使用甲碳环（MC）胸苷（T）的两种异构体，一种是有效的抗疱疹剂，其假糖部分锁定在假旋转循环的北半球（1a，N-MCT），另一种是无活性的异构体，锁定在对映的南半球（S）构象（1b，S-MCT），以确定激酶和聚合酶是否根据糖构象区分它们的底物。对这两种化合物进行了固态和溶液构象分析，并直接测量了对照细胞、感染单纯疱疹病毒的细胞或转染了相应病毒激酶基因（HSV-tk）的细胞中的单磷酸、二磷酸和三磷酸水平，结果表明激酶更喜欢采用S糖构象的底物。另一方面，转染了HSV-tk的小鼠肿瘤细胞系的细胞DNA聚合酶几乎只掺入了锁定的N构象异构体（N-MCTTP）的三磷酸，尽管存在更高水平的S构象异构体三磷酸（S-MCTTP）。
