【摘要】 根据已测定的周质结合蛋白的晶体结构,目前普遍认为第一和第二类周质结合蛋白(Periplasmic Binding Protein,PBP)在结合和释放底物的过程中会发生较大规模的构象变化。比较已测定的同种第三类PBP结合底物前后的晶体结构发现,二者之间的差别极小,因此很多研究者认为第三类PBP的工作机理可能不同于第一、二类PBP。在本工作中,对鼠疫杆菌亚铁血红素(heme)结合蛋白HmuT与另两类heme结合蛋白ShuT和PhuT的结构进行了比较,并利用高斯网络模型与各项异性网络模型方法对亚铁血红素结合蛋白HmuT的功能性运动进行了较为详尽的分析。根据计算结果,认为116-118,148-151,和263-265等三个区域在HmuT的功能性运动中充当铰链区。HmuT在结合heme前后均有围绕铰链区做扭转和开合运动的趋势。综上所述,与ShuT和PhuT相比,尽管HmuT在结构上存在一定的特殊性,HmuT可能依然采取类似的工作机制来捕获和释放heme。更多还原

【Abstract】 According to the determined crystal structures,periplasmic binding proteins(PBPs) of the first and the second classes are generally believed to be very flexible:they can largely change their conformations when binding and releasing subtracts.As far as the PBPs of the third class are concerned,the conformations between the subtract-free and the subtract-bound states are of little difference on the basis of the determined structures.In view of this fact,many researchers believed that the working mechanism adopted by the third class PBPs may be different with that of the first and second class.In order to figure out and working mechanism of the Yersinia pestis heme binding protein (HmuT),we compared the structures of HmuT with those of two other heme PBPs(ShuT and PhuT),and applied Gaussian Network Model and Anisotropic Network Model to analyze its functional motions.According to the results,it is found that residues(?)116-118,148-151 and 263-265 act as hinge regions and HmuT exhibits open-close and twisting motion tendencies relative to the three hinge regions no matter on the heme-free or heme-bound states.Consequently,in spite of the particularity in structure,HmuT may also take the similar working mechanism with that of ShuT and PhuT during the process of capturing and releasing their substrates.更多还原