Determination of the gelsolin binding site on F-actin: implications for severing and capping.
Gelsolin is a six-domain protein that regulates actin assembly by severing, capping, and nucleating filaments. We have used electron cryomicroscopy and helical reconstruction to identify its binding site on F-actin. To obtain fully decorated filaments under severing conditions, we have studied a derivative (G2-6) that has a reduced severing efficiency compared to gelsolin. A three-dimensional reconstruction of G2-6:F-actin was obtained by electron cryomicroscopy and helical reconstruction. The structure shows that gelsolin bridges two longitudinally associated monomers when it binds the filament. The F-actin binding region of G2-6 is centered axially at subdomain 3 and radially between subdomains 1 and 3 of the upper actin monomer. Our results suggest that for severing to occur, both gelsolin and actin undergo large conformational changes.
McGough
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Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030, USA. amcgough@bcm.tmc.edu
Chiu
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Way
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D000199:Actins / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D001665:Binding Sites; D003001:Cloning, Molecular; D004926:Escherichia coli; D005615:Freezing; D018260:Gelsolin / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure
D000199:Actins; D018260:Gelsolin; D008840:Microfilament Proteins; D011994:Recombinant Proteins