Speed R R, Winkler H H
Department of Microbiology and Immunology, University of South Alabama, College of Medicine, Mobile 36688.
J Bacteriol. 1991 Aug;173(15):4902-3. doi: 10.1128/jb.173.15.4902-4903.1991.
Thymidylate biosynthesis via the methylation of dUMP is required for DNA replication in Rickettsia prowazekii, an obligate intracytoplasmic bacterium. In theory, dUMP synthesis could occur either by the deamination of deoxycytidine nucleotides or by the reduction of uridine nucleotides. Accordingly, the incorporation of both radiolabeled cytidine and uridine into the thymidylate of R. prowazekii was examined. After DNA hydrolysis and high-performance liquid chromatography, it was determined that 85% of the rickettsial thymidylate was derived from cytidine and the remaining 15% was derived from uridine. These findings were supported by the identification of a dCTP deaminase activity in extracts of R. prowazekii. Extracts of R. prowazekii deaminated 1.7 +/- 0.3 nmol of dCTP/min/mg of protein (a value calculated to suffice for rickettsial growth), and no measurable activity was observed with dCMP as the substrate.
通过dUMP甲基化进行胸苷酸生物合成是专性胞内细菌普氏立克次体DNA复制所必需的。理论上，dUMP合成可以通过脱氧胞苷核苷酸的脱氨作用或尿苷核苷酸的还原作用发生。因此，研究了放射性标记的胞苷和尿苷掺入普氏立克次体胸苷酸的情况。经过DNA水解和高效液相色谱分析，确定立克次体胸苷酸的85%来源于胞苷，其余15%来源于尿苷。普氏立克次体提取物中dCTP脱氨酶活性的鉴定支持了这些发现。普氏立克次体提取物以1.7±0.3 nmol dCTP/分钟/毫克蛋白质的速度脱氨（该值经计算足以满足立克次体生长），以dCMP为底物时未观察到可测量的活性。
