title: The B-ring substituent at C-7 of colchicine and the alpha-C-terminus of tubulin communicate through the "tail-body" interaction.
abstract: The carboxy terminals of alphabeta-tubulins are flexible regions rich in acidic amino acid residues that play an inhibitory role in the polymerization of tubulin to microtubules. We have shown that the binding of colchicine and its B-ring analogs (with C-7 substituents) to tubulin are pH sensitive and have high activation energies. Under identical conditions, the binding of analogs without C-7 substituents is pH independent and has lower activation energy. Beta-C-terminus-truncated tubulin (alphabeta(s)) shows similar pH sensitivity and activation energy to native tubulin (alphabeta). Removal of the C-termini of both subunits of tubulin (alpha(s)beta(s)) or the binding of a basic peptide P2 to the negatively charged alpha-C-terminus of tubulin causes a colchicine-tubulin interaction independent of pH with a low activation energy. Tubulin dimer structure shows that the C-terminal alpha-tail is too far from the colchicine binding site to interact directly with the bound colchicine. Therefore, it is likely that the interaction of the alpha-C-terminus with the main body of tubulin indirectly affects the colchicine-tubulin interaction via conformational changes in the main body. We therefore conclude that in the presence of tail-body interaction, a B-ring substituent makes contact with the alpha-tubulin and induces significant conformational changes in alpha-tubulin.
authors.affiliation: Department of Biochemistry, Centenary Campus, Bose Institute, Calcutta, India.
authors.forename: Shalmali
authors.initials: S
authors.lastname: Chakraborty
authors.forename: Suvroma
authors.initials: S
authors.lastname: Gupta
authors.forename: Taradas
authors.initials: T
authors.lastname: Sarkar
authors.forename: Asim
authors.initials: A
authors.lastname: Poddar
authors.forename: Jose
authors.initials: J
authors.lastname: Pena
authors.forename: Rafael
authors.initials: R
authors.lastname: Solana
authors.forename: Raquel
authors.initials: R
authors.lastname: Tarazona
authors.forename: Bhabatarak
authors.initials: B
authors.lastname: Bhattacharyya
mesh_terms: D000818:Animals; D003078:Colchicine / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D006041:Goats; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D013816:Thermodynamics; D014404:Tubulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D014404:Tubulin; D003078:Colchicine