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首页> 外文期刊>Biochemistry >Conformational Exchange in Pseudoazurin: Different Kinds of Microsecond to Millisecond Dynamics Characterized by Their pH and Buffer Dependence Using 15N NMR Relaxation
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Conformational Exchange in Pseudoazurin: Different Kinds of Microsecond to Millisecond Dynamics Characterized by Their pH and Buffer Dependence Using 15N NMR Relaxation

机译：伪天青素的构象交换：不同种类的微秒至毫秒动力学，其特征在于其pH和使用15N NMR弛豫的缓冲液依赖性

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摘要

The dynamics of the reduced form of the blue copper protein pseudoazurin from Alcaligenes faecalis S-6 was investigated using 15N relaxation measurements with a focus on the dynamics of the micro- to millisecond time scale. Different types of conformational exchange processes are observed in the protein on this time scale. At low pH, the protonation of the C-terminal copper-ligated histidine, His81, is observed. A comparison of the exchange rates in the presence and absence of added buffers shows that the protonation is the rate-limiting step at low buffer concentrations. This finding agrees with previous observations for other blue copper proteins, e.g., amicyanin and plastocyanin. However, in contrast to plastocyanin but similar to amicyanin, a second conformational exchange between different conformations of the protonated copper site is observed at low pH, most likely triggered by the protonation of His81. This process has been further characterized using CPMG dispersion methods and is found to occur with a rate of a few thousands per second. Finally, micro- to millisecond motions are observed in one of the loop regions and in the α-helical regions. These motions are unaffected by pH and are unrelated to the conformational changes in the active site of pseudoazurin.
机译：使用15N弛豫测量研究了粪便产碱杆菌S-6的蓝色铜蛋白假天青素的还原形式的动力学，重点是微秒级到毫秒级的动力学。在该时间尺度上，在蛋白质中观察到不同类型的构象交换过程。在低pH值下，观察到C端铜连接的组氨酸His81的质子化。在存在和不存在添加缓冲液的情况下，交换速率的比较表明，在低缓冲液浓度下，质子化是限速步骤。这一发现与先前对其他蓝铜蛋白例如花青素和质体蓝素的观察结果一致。但是，与质体蓝蛋白相反，但与花青素相似，在低pH下观察到质子化铜位点不同构象之间的第二种构象交换，这很可能是His81的质子化触发的。使用CPMG分散方法进一步表征了该过程，发现该过程以每秒几千次的速率发生。最后，在其中一个回路区域和α螺旋区域中观察到微秒到毫秒的运动。这些运动不受pH的影响，并且与假天青素活性位点的构象变化无关。

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  • 来源
    《Biochemistry》 |2009年第1期|p.50-58|共9页
  • 作者

    Mathias A. S. Hass Monica D. Vlasie Marcellus Ubbink and Jens J. Led;

  • 作者单位

    Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark, and Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands;

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