A tethered delivery mechanism explains the catalytic action of a microtubule polymerase

Elife. 2014 Aug 5;3:e03069. doi: 10.7554/eLife.03069.

Abstract

Stu2p/XMAP215 proteins are essential microtubule polymerases that use multiple αβ-tubulin-interacting TOG domains to bind microtubule plus ends and catalyze fast microtubule growth. We report here the structure of the TOG2 domain from Stu2p bound to yeast αβ-tubulin. Like TOG1, TOG2 binds selectively to a fully 'curved' conformation of αβ-tubulin, incompatible with a microtubule lattice. We also show that TOG1-TOG2 binds non-cooperatively to two αβ-tubulins. Preferential interactions between TOGs and fully curved αβ-tubulin that cannot exist elsewhere in the microtubule explain how these polymerases localize to the extreme microtubule end. We propose that these polymerases promote elongation because their linked TOG domains concentrate unpolymerized αβ-tubulin near curved subunits already bound at the microtubule end. This tethering model can explain catalyst-like behavior and also predicts that the polymerase action changes the configuration of the microtubule end.

Keywords: TOG domain; X-ray structure; conformation-selective; kinetic simulation; microtubule.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / chemistry
  • Caenorhabditis elegans Proteins / genetics*
  • Caenorhabditis elegans Proteins / metabolism
  • Catalytic Domain
  • Genetic Complementation Test
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / genetics*
  • Microtubule-Associated Proteins / metabolism
  • Microtubules / chemistry*
  • Microtubules / metabolism
  • Models, Molecular
  • Protein Binding
  • Protein Interaction Domains and Motifs
  • Protein Isoforms / chemistry
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Structure, Secondary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Tubulin / chemistry
  • Tubulin / genetics*
  • Tubulin / metabolism
  • Xenopus Proteins / chemistry
  • Xenopus Proteins / genetics*
  • Xenopus Proteins / metabolism
  • Xenopus laevis / genetics
  • Xenopus laevis / metabolism

Substances

  • CKAP5 protein, Xenopus
  • Caenorhabditis elegans Proteins
  • Microtubule-Associated Proteins
  • Protein Isoforms
  • Recombinant Proteins
  • STU2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Tubulin
  • Xenopus Proteins

Associated data

  • PDB/4U3J