Breece Robert M, Hu Zhenxin, Bennett Brian, Crowder Michael W, Tierney David L
Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
J Am Chem Soc. 2009 Aug 26;131(33):11642-3. doi: 10.1021/ja902534b.
We report rapid-freeze-quench X-ray absorption spectroscopy of a dizinc metallo-beta-lactamase (MbetaL) reaction intermediate. The Zn(II) ions in the dinuclear active site of the S. maltophilia Class B3 MbetaL move away from each other, by approximately 0.3 A after 10 ms of reaction with nitrocefin, from 3.4 to 3.7 A. Together with our previous characterization of the resting enzyme and its nitrocefin product complex, where the Zn(II) ion separation relaxes to 3.6 A, these data indicate a scissoring motion of the active site that accompanies the ring-opening step. The average Zn(II) coordination number of 4.5 in the resting enzyme appears to be maintained throughout the reaction with nitrocefin. This is the first direct structural information available on early stage dizinc metallo-beta-lactamase catalysis.
我们报道了一种双锌金属β-内酰胺酶(MbetaL)反应中间体的快速冷冻淬灭X射线吸收光谱。嗜麦芽窄食单胞菌B3类MbetaL双核活性位点中的Zn(II)离子在与头孢硝噻吩反应10毫秒后彼此远离,从3.4埃移动到3.7埃,距离增加约0.3埃。结合我们之前对静息酶及其头孢硝噻吩产物复合物的表征,其中Zn(II)离子间距松弛至3.6埃,这些数据表明活性位点存在伴随开环步骤的剪式运动。静息酶中平均4.5的Zn(II)配位数在与头孢硝噻吩的整个反应过程中似乎保持不变。这是关于双锌金属β-内酰胺酶催化早期阶段的首个直接结构信息。