Structural basis for high-affinity actin binding revealed by a β-III-spectrin SCA5 missense mutation

Spinocerebellar ataxia type 5 (SCA5) is a neurodegenerative disease caused by mutations in the cytoskeletal protein β-III-spectrin. Previously, a SCA5 mutation resulting in a leucine-to-proline substitution (L253P) in the actin-binding domain (ABD) was shown to cause a 1000-fold increase in actin-bi...

Full description

Saved in:
Bibliographic Details
Published in:Nature communications 2017-11, Vol.8 (1), p.1350-7, Article 1350
Main Authors: Avery, Adam W., Fealey, Michael E., Wang, Fengbin, Orlova, Albina, Thompson, Andrew R., Thomas, David D., Hays, Thomas S., Egelman, Edward H.
Format: Article
Language:English
Subjects:
631/45/535/1258/1259
631/57/2272/2273
Actin
Affinity
Ataxia
Binding
Cytoskeleton
Humanities and Social Sciences
Leucine
Missense mutation
multidisciplinary
Mutation
Proline
Proteins
Science
Science (multidisciplinary)
Sedimentation
Spectrin
Spinocerebellar ataxia
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Spinocerebellar ataxia type 5 (SCA5) is a neurodegenerative disease caused by mutations in the cytoskeletal protein β-III-spectrin. Previously, a SCA5 mutation resulting in a leucine-to-proline substitution (L253P) in the actin-binding domain (ABD) was shown to cause a 1000-fold increase in actin-binding affinity. However, the structural basis for this increase is unknown. Here, we report a 6.9 Å cryo-EM structure of F-actin complexed with the L253P ABD. This structure, along with co-sedimentation and pulsed-EPR measurements, demonstrates that high-affinity binding caused by the CH2-localized mutation is due to opening of the two CH domains. This enables CH1 to bind actin aided by an unstructured N-terminal region that becomes α-helical upon binding. This helix is required for association with actin as truncation eliminates binding. Collectively, these results shed light on the mechanism by which β-III-spectrin, and likely similar actin-binding proteins, interact with actin, and how this mechanism can be perturbed to cause disease. The disease causing L253P mutation in the actin-binding domain (ABD) of β-III-spectrin drastically increases actin-binding affinity. Here, the authors present the cryo-EM structure of F-actin complexed with the ABD mutant and double electron–electron resonance measurements show how the mutation affects the ABD conformational state.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-017-01367-w