tailieunhanh - Báo cáo khóa học: Different associational and conformational behaviors between the second and third repeat fragments in the tau microtubule-binding domain

The third repeat fragment (R3) in the four-repeat micro-tubule-binding domain of the water-soluble tau protein has been considered to play an essential role in the protein’s filamentous assembly. To clarify the associational and con-formational features that differentiate R3 from the second repeat, R2, the heparin-induced assembly profiles of these peptide fragments were monitored by the thioflavin fluor-escence method and electron microscopy. | Eur. J. Biochem. 271 545-552 2004 FEBS 2004 doi Different associational and conformational behaviors between the second and third repeat fragments in the tau microtubule-binding domain Katsuhiko Minoura1. Tian-Mina Yao1 Koji Tomoo1 Miho Sumida2. Masahiro Sasaki2 Taizo Taniauchi2 3 and Toshimasa Ishida1 1 Osaka University of Pharmaceutical Sciences Takatsuki Osaka Japan 2Behavioral and Medical Sciences Research Consortium Akashi Hyogo Japan 3Biosignal Research Center Kobe University Kobe Japan The third repeat fragment R3 in the four-repeat microtubule-binding domain of the water-soluble tau protein has been considered to play an essential role in the protein s filamentous assembly. To clarify the associational and conformational features that differentiate R3 from the second repeat R2 the heparin-induced assembly profiles of these peptide fragments were monitored by the thioflavin fluorescence method and electron microscopy. The trifluoroethanol-induced reversible conformational change from a random structure to an a-helical structure in an aqueous solution was monitored by CD measurement and the structure of R2 in trifluoroethanol solution was analyzed by a combination of two-dimensional 1H-NMR measurements and molecular modeling calculations to facilitate comparison with the structure of R3. The speed of R3 assembly was remarkably faster than that of R2 in spite of their similar amino acid sequences. The averaged NMR conformers of R2 exhibited the whole-spanning a-helical structure. Similar features observed in R2 and R3 conformers in trifluoroethanol were that the Leu10-Leu20 Lys20 sequence takes a helical structure with the amphipathic-like distribution of the respective side-chains whereas the C-terminal moieties are both flexible. In contrast a notable difference was observed at the N-terminal Val1-Lys6 sequence namely a helical conformation for R2 and an extended conformation for R3. These conformational behaviors would be .