Löwe J, Stock D, Jap B, Zwickl P, Baumeister W, Huber R
Max-Planck-Institut für Biochemie, Abteilung für Strukturforschung, Martinsried, Germany.
Science. 1995 Apr 28;268(5210):533-9. doi: 10.1126/science.7725097.
The three-dimensional structure of the proteasome from the archaebacterium Thermoplasma acidophilum has been elucidated by x-ray crystallographic analysis by means of isomorphous replacement and cyclic averaging. The atomic model was built and refined to a crystallographic R factor of 22.1 percent. The 673-kilodalton protease complex consists of 14 copies of two different subunits, alpha and beta, forming a barrel-shaped structure of four stacked rings. The two inner rings consist of seven beta subunits each, and the two outer rings consist of seven alpha subunits each. A narrow channel controls access to the three inner compartments. The alpha 7 beta 7 beta 7 alpha 7 subunit assembly has 72-point group symmetry. The structures of the alpha and beta subunits are similar, consisting of a core of two antiparallel beta sheets that is flanked by alpha helices on both sides. The binding of a peptide aldehyde inhibitor marks the active site in the central cavity at the amino termini of the beta subunits and suggests a novel proteolytic mechanism.
通过同晶置换和循环平均法的X射线晶体学分析，已阐明了嗜热栖热菌蛋白酶体的三维结构。构建了原子模型并将其精修至晶体学R因子为22.1%。这个673千道尔顿的蛋白酶复合体由两种不同亚基（α和β）的14个拷贝组成，形成一个由四个堆叠环组成的桶状结构。两个内环各由七个β亚基组成，两个外环各由七个α亚基组成。一条狭窄的通道控制着进入三个内部隔室的通路。α7β7β7α7亚基组装体具有72点群对称性。α和β亚基的结构相似，由两个反平行β折叠片的核心组成，两侧均有α螺旋。肽醛抑制剂的结合标记了β亚基氨基末端中央腔内的活性位点，并提示了一种新的蛋白水解机制。
