A discrete repeated sequence defines a tubulin binding domain on microtubule-associated protein tau

Abstract

The protein domain responsible for the interaction of tau with tubulin has been identified. Biophysical studies indicated that the synthetic peptide Val 187Gly 204 (VRSKIGSTENLKHQPGGG) from the repetitive sequence on tau binds to two sites on the tubulin heterodimer and to one site on each of the microtubule-associated protein-interacting C-terminal tubulin peptides α(430–441) and β(422–434). The binding data showed a relatively stronger interaction of Val 187-Gly 204 with β(422–434) as compared to that with α(430–441). The interaction of this tau peptide with either α or β tubulin peptides appears to be associated with conformational changes in both the tau and the tubulin peptides. The β tubulin peptide also appears to induce a structural change of tau fragment Val 218Gly 235. Interestingly, tau peptides Val 187Gly 204 and Val 218Gly 235 induced tubulin self-assembly in a cold-reversible fashion, and incorporated into the assembled polymers. The specificity of the interaction of the tau peptide was supported by the competition of tau protein for the interaction with the tubulin polymer. In addition, the tau peptide appears to contain the principal antigenic determinant(s) recognized by antiidiotypic antibodies that react with the tubulin binding domains on microtubule-associated proteins. The present findings together with the demonstration of the presence of multiple sites for the binding of the α(430–441) and β(422–434) tubulin fragments to tau, and the existence of repetitive sequences on tau, strongly support the hypothesis that the region of tau defined by the repetitive sequences is involved in its interaction with tubulin.