Structure of the ACF7 EF-Hand-GAR Module and Delineation of Microtubule Binding Determinants

Structure. 2017 Jul 5;25(7):1130-1138.e6. doi: 10.1016/j.str.2017.05.006. Epub 2017 Jun 8.


Spectraplakins are large molecules that cross-link F-actin and microtubules (MTs). Mutations in spectraplakins yield defective cell polarization, aberrant focal adhesion dynamics, and dystonia. We present the 2.8 Å crystal structure of the hACF7 EF1-EF2-GAR MT-binding module and delineate the GAR residues critical for MT binding. The EF1-EF2 and GAR domains are autonomous domains connected by a flexible linker. The EF1-EF2 domain is an EFβ-scaffold with two bound Ca2+ ions that straddle an N-terminal α helix. The GAR domain has a unique α/β sandwich fold that coordinates Zn2+. While the EF1-EF2 domain is not sufficient for MT binding, the GAR domain is and likely enhances EF1-EF2-MT engagement. Residues in a conserved basic patch, distal to the GAR domain's Zn2+-binding site, mediate MT binding.

Keywords: ACF7; EF Hand; GAR; Gas2; MACF1; actin; microtubule; spectraplakin.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Binding Sites
  • EF Hand Motifs
  • HEK293 Cells
  • Humans
  • Microfilament Proteins / chemistry*
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism
  • Microtubules / metabolism*
  • Mutation
  • Protein Binding
  • Zinc / metabolism


  • MACF1 protein, human
  • Microfilament Proteins
  • Zinc