A structural model for microtubule minus-end recognition and protection by CAMSAP proteins

Nat Struct Mol Biol. 2017 Nov;24(11):931-943. doi: 10.1038/nsmb.3483. Epub 2017 Oct 9.

Abstract

CAMSAP and Patronin family members regulate microtubule minus-end stability and localization and thus organize noncentrosomal microtubule networks, which are essential for cell division, polarization and differentiation. Here, we found that the CAMSAP C-terminal CKK domain is widely present among eukaryotes and autonomously recognizes microtubule minus ends. Through a combination of structural approaches, we uncovered how mammalian CKK binds between two tubulin dimers at the interprotofilament interface on the outer microtubule surface. In vitro reconstitution assays combined with high-resolution fluorescence microscopy and cryo-electron tomography suggested that CKK preferentially associates with the transition zone between curved protofilaments and the regular microtubule lattice. We propose that minus-end-specific features of the interprotofilament interface at this site serve as the basis for CKK's minus-end preference. The steric clash between microtubule-bound CKK and kinesin motors explains how CKK protects microtubule minus ends against kinesin-13-induced depolymerization and thus controls the stability of free microtubule minus ends.

MeSH terms

  • Cryoelectron Microscopy
  • Electron Microscope Tomography
  • Eukaryota
  • Kinesin / antagonists & inhibitors*
  • Microscopy, Fluorescence
  • Microtubule-Associated Proteins / chemistry*
  • Microtubule-Associated Proteins / metabolism*
  • Microtubules / metabolism*
  • Protein Binding

Substances

  • Microtubule-Associated Proteins
  • Kinesin