Mayer M P, Schröder H, Rüdiger S, Paal K, Laufen T, Bukau B
Institut für Biochemie und Molekularbiologie, Universität Freiburg, Hermann-Herder-Str.7, 79104 D-Freiburg, Germany.
Nat Struct Biol. 2000 Jul;7(7):586-93. doi: 10.1038/76819.
The 70 kDa heat shock proteins (the Hsp70 family) assist refolding of their substrates through ATP-controlled binding. We have analyzed mutants of DnaK, an Hsp70 homolog, altered in key residues of its substrate binding domain. Substrate binding occurs by a dynamic mechanism involving: a hydrophobic pocket for a single residue that is crucial for affinity, a two-layered closing device involving independent action of an alpha-helical lid and an arch, and a superimposed allosteric mechanism of ATP-controlled opening of the substrate binding cavity that operates largely through a beta-structured subdomain. Correlative evidence from mutational analysis suggests that the ADP and ATP states of DnaK differ in the frequency of the conformational changes in the alpha-helical lid and beta-domain that cause opening of the substrate binding cavity. The affinity for substrates, as defined by this mechanism, determines the efficiency of DnaJ-mediated and ATP hydrolysis mediated locking-in of substrates and chaperone activity of DnaK.
70 kDa热休克蛋白（Hsp70家族）通过ATP控制的结合来协助其底物重新折叠。我们分析了DnaK（一种Hsp70同源物）的突变体，其底物结合结构域的关键残基发生了改变。底物结合通过一种动态机制发生，该机制包括：一个对亲和力至关重要的单个残基的疏水口袋、一个涉及α-螺旋盖和拱形独立作用的两层关闭装置，以及一种主要通过β-结构亚结构域起作用的ATP控制的底物结合腔开放的叠加变构机制。来自突变分析的相关证据表明，DnaK的ADP和ATP状态在导致底物结合腔开放的α-螺旋盖和β-结构域构象变化的频率上有所不同。由该机制定义的对底物的亲和力决定了DnaJ介导的以及ATP水解介导的底物锁定效率和DnaK的伴侣活性。
