MICROTUBULE MINUS ENDS CAN BE LABELED WITH A PHAGE DISPLAY ANTIBODY SPECIFIC TO ALPHA-TUBULIN

To investigate the orientation of alpha- and beta-tubulin heterodimers within microtubules, we cloned a phage display antibody to alpha-tubu lin. The N-terminal 100 residues of alpha-tubulin were bacterially exp ressed and used to select clones from a large repertoire of antibody-e xpressing phagemid particles. One clone reacted with the expressed alp ha-tubulin N terminus and native tubulin dimer but not with the expres sed beta-tubulin N terminus. Electron microscopy showed 30 nm gold bea ds coated with die antibody binding to one end of brain microtubules. The beads bound to the minus ends of axonemes but not to the brain tub ulin extensions from their plus ends. In sliding motility assays with a plus end directed motor, beads were pushed ahead of the microtubules . Our results indicate that an N-terminal epitope of alpha-tubulin is exposed only at the minus ends of microtubules. (C) 1996 Academic Pres s Limited