Tubulin subunit carboxyl termini determine polymerization efficiency.
Cleavage of tubulin by subtilisin removes a small (Mr less than 2000) fragment from the C-terminal end of both alpha and beta subunits. The resulting protein is much reduced in negative charge. The cleaved, less acidic protein retains its competence to polymerize in a GTP-dependent and cold-, GDP-, and podophyllotoxin-sensitive manner and assembles into sheets or bundles of twisted filaments. The critical concentration for polymerization of the cleaved protein is about 50-fold lower than that for intact tubulin. It is proposed that the C termini of the subunits normally impede polymerization.
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology; D007700:Kinetics; D046911:Macromolecular Substances; D008854:Microscopy, Electron; D011034:Podophyllotoxin / Q000494:pharmacology; D051381:Rats; D014404:Tubulin / Q000378:metabolism*
D046911:Macromolecular Substances; D014404:Tubulin; D000244:Adenosine Diphosphate; D006160:Guanosine Triphosphate; D011034:Podophyllotoxin