Angiotensin II Analogues. Part II. Synthesis and incorporation of the sulfur-containing aromatic amino acids:L-(4?-SH)Phe,L-(4?-SO2NH2)Phe,L-(4?-SO3?)Phe andL-(4?-S-CH3)Phe
作者:Emanuel Escher、Michel Bernier、Paul Parent
DOI:10.1002/hlca.19830660504
日期:1983.7.27
L-Phenylalanine has been treated with chlorosulfonic acid and the product was either hydrolyzed, ammonolyzed or reduced. The resulting sulfonic-acid and aminosulfonyl derivatives have been employed for peptide synthesis with Boc-protection of the Nα-position only. The reduction product L-(4′-SH)Phe has been protected by formation of asymmetric disulfides or with various thiol protecting groups (benzyl-
<i>p</i>-Thiophenylalanine-Induced DNA Cleavage and Religation Activity of a Modified Vaccinia Topoisomerase IB
作者:Shengxi Chen、Yi Zhang、Sidney M. Hecht
DOI:10.1021/bi201291p
日期:2011.11.1
chemically misacylated tRNA. The modification, which resulted in replacement of the nucleophilic tyrosine OH group with SH, retained DNA topoisomerase activity and did not alter the DNAcleavage site. However, the modified topoisomerase effected relaxation of supercoiled plasmid DNA at a rate about 16-fold slower than the wild-type enzyme. The thiophenylalanine-induced DNAcleavage rate (kcl = 1 × 10–4 s–1)
牛痘DNA拓扑异构酶IB是IB型拓扑异构酶中最小的。由于其体积小(314个氨基酸)和靶位点特异性(5'(C / T)CCTTp ↓位点),它是研究IB型酶与双链DNA相互作用的极佳模型。在这项研究中,通过体外将对-硫代苯丙氨酸掺入酶的活性位点(274位)在化学错误酰化的tRNA存在下进行翻译。修饰导致亲核酪氨酸OH基团被SH取代,保留了DNA拓扑异构酶活性,并且没有改变DNA切割位点。然而,修饰的拓扑异构酶以比野生型酶慢约16倍的速率实现超螺旋质粒DNA的松弛。硫代苯丙氨酸诱导的DNA裂解率(k cl = 1×10 –4 s –1)比野生型酶(k cl = 3×10 –3 s –1)低30倍。)。相反,硫代苯丙氨酸诱导的DNA连接比野生型酶更快。我们认为动力学的变化反映了在野生型和修饰酶催化的反应中形成和破坏的OP和S-P键之间键能的差异。我们还研究了向野生型和修饰的拓扑异构酶I中添加Mg