Dynamics of Dystrophin's Actin-Binding Domain

Michael E. Fealey, Benjamin Horn, Christian Coffman, Robert Miller, Ava Y. Lin, Andrew R Thompson, Justine Schramel, Erin Groth, Anne Hinderliter, Alessandro Cembran, David D Thomas

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

We have used pulsed electron paramagnetic resonance, calorimetry, and molecular dynamics simulations to examine the structural mechanism of binding for dystrophin's N-terminal actin-binding domain (ABD1) and compare it to utrophin's ABD1. Like other members of the spectrin superfamily, dystrophin's ABD1 consists of two calponin-homology (CH) domains, CH1 and CH2. Several mutations within dystrophin's ABD1 are associated with the development of severe degenerative muscle disorders Duchenne and Becker muscular dystrophies, highlighting the importance of understanding its structural biology. To investigate structural changes within dystrophin ABD1 upon binding to actin, we labeled the protein with spin probes and measured changes in inter-CH domain distance using double-electron electron resonance. Previous studies on the homologous protein utrophin showed that actin binding induces a complete structural opening of the CH domains, resulting in a highly ordered ABD1-actin complex. In this study, double-electron electron resonance shows that dystrophin ABD1 also undergoes a conformational opening upon binding F-actin, but this change is less complete and significantly more structurally disordered than observed for utrophin. Using molecular dynamics simulations, we identified a hinge in the linker region between the two CH domains that grants conformational flexibility to ABD1. The conformational dynamics of both dystrophin's and utrophin's ABD1 showed that compact conformations driven by hydrophobic interactions are preferred and that extended conformations are energetically accessible through a flat free-energy surface. Considering that the binding free energy of ABD1 to actin is on the order of 6–7 kcal/mole, our data are compatible with a mechanism in which binding to actin is largely dictated by specific interactions with CH1, but fine tuning of the binding affinity is achieved by the overlap between conformational ensembles of ABD1 free and bound to actin.

Original languageEnglish (US)
Pages (from-to)445-454
Number of pages10
JournalBiophysical journal
Volume115
Issue number3
DOIs
StatePublished - Aug 7 2018

Bibliographical note

Funding Information:
This work was supported in part by National Institutes of Health grant R37 AG026160 to D.D.T. This material is based upon work supported by the National Science Foundation grant No. MCB-1616854 to A.H., A.C., and D.D.T. M.E.F. was supported by National Institutes of Health Training Grant T32 AR007612. EPR experiments were performed at the Biophysical Technology Center, University of Minnesota. Computational resources were provided by the Minnesota Supercomputing Institute.

Funding Information:
This work was supported in part by National Institutes of Health grant R37 AG026160 to D.D.T. This material is based upon work supported by the National Science Foundation grant No. MCB-1616854 to A.H., A.C., and D.D.T. M.E.F. was supported by National Institutes of Health Training Grant T32 AR007612 . EPR experiments were performed at the Biophysical Technology Center, University of Minnesota. Computational resources were provided by the Minnesota Supercomputing Institute.

Publisher Copyright:
© 2018 Biophysical Society

Fingerprint Dive into the research topics of 'Dynamics of Dystrophin's Actin-Binding Domain'. Together they form a unique fingerprint.

Cite this