Tubulin polymers and their pull-downs from cultured cells. (A) Schematic of the protocol for finding curl-binding proteins. (i) Mean of 47 KMTs from metaphase PtK cells, showing a fibril (arrow) connecting chromatin to a bending protofilament. (ii) A tubulin curl made with vinblastine. (iii) Mitotic U2OS cells used to make cell extracts. (iv) Symbolic representation of sedimenting proteins from extracts with tubulin curls. (vi) Symbolic representation of desalting proteins in a spin column. (vii) Cellular proteins are separated into those that bind Tx-MTs (pellet) and those that prefer curls (supernatant). (B) SDS-PAGE of the tubulin used to make pull-down ligands, as eluted from a phosphocellulose column, and molecular mass markers. (C) electron micrograph of negatively stained, vinblastine-induced tubulin curls; (D) a comparable image of Tx-MTs. (E) SDS-PAGE gels of molecular mass markers, cell lysates (L) from log-phase or synchronized cells, followed by the proteins pulled down from the extracts by curls (C) or Tx-MTs (Tx), as described in A.