Structural Basis of Actin Filament Nucleation by Tandem W Domains
Xiaorui Chen,
Fengyun Ni,
Xia Tian,
Elena Kondrashkina,
Qinghua Wang,
Jianpeng Ma
Affiliations
Xiaorui Chen
Graduate Program of Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
Fengyun Ni
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
Xia Tian
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
Elena Kondrashkina
Life Sciences Collaborative Access Team (LS-CAT), Synchrotron Research Center, Northwestern University, Argonne, IL 60439, USA
Qinghua Wang
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
Jianpeng Ma
Graduate Program of Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
Spontaneous nucleation of actin is very inefficient in cells. To overcome this barrier, cells have evolved a set of actin filament nucleators to promote rapid nucleation and polymerization in response to specific stimuli. However, the molecular mechanism of actin nucleation remains poorly understood. This is hindered largely by the fact that actin nucleus, once formed, rapidly polymerizes into filament, thus making it impossible to capture stable multisubunit actin nucleus. Here, we report an effective double-mutant strategy to stabilize actin nucleus by preventing further polymerization. Employing this strategy, we solved the crystal structure of AMPPNP-actin in complex with the first two tandem W domains of Cordon-bleu (Cobl), a potent actin filament nucleator. Further sequence comparison and functional studies suggest that the nucleation mechanism of Cobl is probably shared by the p53 cofactor JMY, but not Spire. Moreover, the double-mutant strategy opens the way for atomic mechanistic study of actin nucleation and polymerization.
