Zhu X, Zhao X, Burkholder W F, Gragerov A, Ogata C M, Gottesman M E, Hendrickson W A
Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York 10032, USA.
Science. 1996 Jun 14;272(5268):1606-14. doi: 10.1126/science.272.5268.1606.
DnaK and other members of the 70-kilodalton heat-shock protein (hsp70) family promote protein folding, interaction, and translocation, both constitutively and in response to stress, by binding to unfolded polypeptide segments. These proteins have two functional units: a substrate-binding portion binds the polypeptide, and an adenosine triphosphatase portion facilitates substrate exchange. The crystal structure of a peptide complex with the substrate-binding unit of DnaK has now been determined at 2.0 angstroms resolution. The structure consists of a beta-sandwich subdomain followed by alpha-helical segments. The peptide is bound to DnaK in an extended conformation through a channel defined by loops from the beta sandwich. An alpha-helical domain stabilizes the complex, but does not contact the peptide directly. This domain is rotated in the molecules of a second crystal lattice, which suggests a model of conformation-dependent substrate binding that features a latch mechanism for maintaining long lifetime complexes.
DnaK及70千道尔顿热休克蛋白（hsp70）家族的其他成员，通过与未折叠的多肽片段结合，在基础状态及应激状态下促进蛋白质折叠、相互作用及转运。这些蛋白质有两个功能单元：一个底物结合部分结合多肽，一个三磷酸腺苷酶部分促进底物交换。现已确定了一个与DnaK底物结合单元形成的肽复合物的晶体结构，分辨率为2.0埃。该结构由一个β-折叠亚结构域和随后的α-螺旋片段组成。肽通过由β-折叠的环所界定的通道以伸展构象与DnaK结合。一个α-螺旋结构域稳定复合物，但不直接接触肽。该结构域在第二个晶格的分子中发生旋转，这提示了一种构象依赖性底物结合模型，其特征是具有维持长寿命复合物的闩锁机制。
