Mizushima Fumie, Minoura Katsuhiko, Tomoo Koji, Sumida Miho, Taniguchi Taizo, Ishida Toshimasa
Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
Biochem Biophys Res Commun. 2006 May 12;343(3):712-8. doi: 10.1016/j.bbrc.2006.02.185. Epub 2006 Mar 10.
To clarify the contribution of the three- or four-repeated peptide moiety in tau microtubule-binding domain (MBD) to paired helical filament (PHF) formation, conformational transition accompanied by heparin-induced filament formation was investigated stepwise for four repeat peptides (R1-R4), one three-repeated R1-R3-R4 peptide (3RMBD), and one four-repeated R1-R2-R3-R4 peptide (4RMBD) using a combination of thioflavin S fluorescence and circular dichroism (CD) measurements in a neutral buffer (pH 7.6). The comparison of the fluorescence profile of each repeat peptide with those of 3RMBD and 4RMBD showed the synergistic contribution of R1-R4 to PHF formation of MBD. The CD spectrum measured as a function of filament formation time indicates that: (i) two conformational transitions occur for the filament formations of R3 (from the random structure to the beta-sheet structure) and 3RMBD (from the random structure to the alpha-helix structure), (ii) the filament formations of R2 and 4RMBD proceed via the synchronized conformational transitions of the alpha-helix and random structures, and (iii) the filament formation of 4RMBD is dependent on the aggregation behavior of R2. These data are useful for elucidating the MBD conformational transition in tau PHF formation.
为阐明tau微管结合域（MBD）中三重复或四重复肽部分对双螺旋丝（PHF）形成的贡献，使用硫黄素S荧光和圆二色性（CD）测量相结合的方法，在中性缓冲液（pH 7.6）中对四个重复肽（R1-R4）、一个三重复的R1-R3-R4肽（3RMBD）和一个四重复的R1-R2-R3-R4肽（4RMBD）逐步研究了肝素诱导的丝形成过程中伴随的构象转变。将每个重复肽的荧光谱与3RMBD和4RMBD的荧光谱进行比较，结果显示R1-R4对MBD的PHF形成具有协同作用。作为丝形成时间函数测量的CD光谱表明：（i）R3的丝形成（从无规结构转变为β-折叠结构）和3RMBD的丝形成（从无规结构转变为α-螺旋结构）发生了两个构象转变；（ii）R2和4RMBD的丝形成通过α-螺旋结构和无规结构的同步构象转变进行；（iii）4RMBD的丝形成取决于R2的聚集行为。这些数据有助于阐明tau PHF形成过程中的MBD构象转变。
