title: A common amino acid sequence in 190-kDa microtubule-associated protein and tau for the promotion of microtubule assembly.
abstract: Previously we reported that chymotryptic fragments of bovine adrenal 190-kDa microtubule-associated proteins (27-kDa fragment) and bovine brain tau (14-kDa fragment) contained microtubule-binding domain (Aizawa, H., Murofushi, H., Kotani, Hisanaga, S., Hirokawa, N., and Sakai, H. (1987) J. Biol. Chem. 262, 3782-3787; Aizawa, H., Kawasaki, H., Murofushi, H., Kotani, S., Suzuki, K., and Sakai, H. (1988) J. Biol. Chem. 263, 7703-7707). In order to study the structure of microtubule-binding domain of the two microtubule-associated proteins, we analyzed the amino acid sequence of the 27-kDa fragment and compared the sequence with that of the 14-kDa fragment. This revealed that 190-kDa microtubule-associated protein and tau contained at least one common sequence of 20 amino acid residues in their microtubule-binding domains. A synthetic polypeptide corresponding to the common sequence (Lys-Asn-Val-Arg-Ser-Lys-Val-Gly-Ser-Thr-Glu-Asn-Ile-Lys- His-Gln-Pro-Gly-Gly-Gly-Arg-Ala-Lys) was bound to microtubules competitively with the 190-kDa MAP. The apparent dissociation constant (KD) for the binding of the polypeptide to microtubules was estimated to be 1.8 x 10(-4) M, and the maximum binding reached 1.2 mol of the synthetic polypeptide/mol of tubulin dimer. This synthetic polypeptide increased the rate and extent of tubulin polymerization and decreased the critical concentration of tubulin for polymerization. The polypeptide-induced tubulin polymers were morphologically normal microtubules and were disassembled by cold treatment. The common sequence (termed assembly-promoting sequence) was thus identified as the active site of 190-kDa microtubule-associated protein and tau for the promotion of microtubule assembly. The reconstitution system of microtubules with this synthetic polypeptide with assembly-promoting sequence may be useful to elucidate detailed molecular mechanism of the promotion of microtubule assembly by microtubule-associated proteins.
authors.affiliation: Department of Biophysics and Biochemistry, Faculty of Science, University of Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Aizawa
authors.forename: H
authors.initials: H
authors.lastname: Kawasaki
authors.forename: H
authors.initials: H
authors.lastname: Murofushi
authors.forename: S
authors.initials: S
authors.lastname: Kotani
authors.forename: K
authors.initials: K
authors.lastname: Suzuki
authors.forename: H
authors.initials: H
authors.lastname: Sakai
mesh_terms: D000311:Adrenal Glands / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D002417:Cattle; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism; D016875:tau Proteins
chemical_list: D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D016875:tau Proteins