作者:Liuhong Chen、Elena Cressina、Neil Dixon、Karl Erixon、Kwasi Agyei-Owusu、Jason Micklefield、Alison G. Smith、Chris Abell、Finian J. Leeper
DOI:10.1039/c2ob07116a
日期:——
The Escherichia coli thiM riboswitch forms specific contacts with its natural ligand, thiamine pyrophosphate (TPP or thiamine diphosphate), allowing it to generate not only nanomolar binding affinity, but also a high degree of discrimination against similar small molecules. A range of synthetic TPP analogues have been used to probe each of the riboswitchâligand interactions. The results show that the pyrimidine-sensing helix of thiM is exquisitely tuned to select for TPP by recognising the H-bonding donor and acceptors around its aminopyrimidine ring and also by forming Ï-stacking interactions that may be sensitive to the electronics of the ring. The central thiazolium ring of TPP appears to be more important for ligand recognition than previously thought. It may contribute to binding via long-range electrostatic interactions and/or by exerting an electron withdrawing effect on the pyrimidine ring, allowing its presence to be sensed indirectly and thereby allowing discrimination between thiamine (and its phosphate esters) and other aminopyrimidines found in vivo. The pyrophosphate moiety is essential for submicromolar binding affinity, but unexpectedly, it does not appear to be strictly necessary for modulation of gene expression.
大肠杆菌中的thiM核糖开关能够与其天然配体硫胺素焦磷酸(TPP或硫胺素二磷酸)形成特异性接触,不仅能够产生纳摩尔级的结合亲和力,还能对类似的小分子展现出高度选择性。一系列合成的TPP类似物被用来探究核糖开关与配体之间的相互作用。结果显示,thiM的嘧啶感知螺旋经过精妙调整,通过识别其氨基嘧啶环周围的氢键供体和受体,以及可能对环电子性质敏感的π堆积相互作用,来选择TPP。TPP的中心噻唑环在配体识别中的重要性似乎比之前认为的更高。它可能通过长程静电相互作用和/或通过对嘧啶环施加电子 withdrawing 效应来促进结合,使得其存在能够被间接感知,从而在体内区分硫胺素(及其磷酸酯)与其他氨基嘧啶。焦磷酸部分对于亚微摩尔级的结合亲和力至关重要,但出乎意料的是,它似乎并不严格需要调控基因表达。