Zheng Ning, Schulman Brenda A, Song Langzhou, Miller Julie J, Jeffrey Philip D, Wang Ping, Chu Claire, Koepp Deanna M, Elledge Stephen J, Pagano Michele, Conaway Ronald C, Conaway Joan W, Harper J Wade, Pavletich Nikola P
Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.
Nature. 2002 Apr 18;416(6882):703-9. doi: 10.1038/416703a.
SCF complexes are the largest family of E3 ubiquitin-protein ligases and mediate the ubiquitination of diverse regulatory and signalling proteins. Here we present the crystal structure of the Cul1-Rbx1-Skp1-F boxSkp2 SCF complex, which shows that Cul1 is an elongated protein that consists of a long stalk and a globular domain. The globular domain binds the RING finger protein Rbx1 through an intermolecular beta-sheet, forming a two-subunit catalytic core that recruits the ubiquitin-conjugating enzyme. The long stalk, which consists of three repeats of a novel five-helix motif, binds the Skp1-F boxSkp2 protein substrate-recognition complex at its tip. Cul1 serves as a rigid scaffold that organizes the Skp1-F boxSkp2 and Rbx1 subunits, holding them over 100 A apart. The structure suggests that Cul1 may contribute to catalysis through the positioning of the substrate and the ubiquitin-conjugating enzyme, and this model is supported by Cul1 mutations designed to eliminate the rigidity of the scaffold.
SCF复合物是E3泛素蛋白连接酶中最大的家族，介导多种调节蛋白和信号蛋白的泛素化。本文展示了Cul1-Rbx1-Skp1-F boxSkp2 SCF复合物的晶体结构，该结构表明Cul1是一种细长的蛋白质，由一个长柄和一个球状结构域组成。球状结构域通过分子间β折叠与RING指蛋白Rbx1结合，形成一个招募泛素结合酶的二亚基催化核心。由一个新型五螺旋基序的三个重复序列组成的长柄，在其末端结合Skp1-F boxSkp2蛋白底物识别复合物。Cul1作为一个刚性支架，组织Skp1-F boxSkp2和Rbx1亚基，使它们相隔超过100埃。该结构表明，Cul1可能通过底物和泛素结合酶的定位促进催化作用，旨在消除支架刚性的Cul1突变支持了这一模型。
