tailieunhanh - Báo cáo khoa học: Structure of amyloid b fragments in aqueous environments

Conformational studies on amyloidb peptide (Ab) in aqueous solution are complicated by its tendency to aggregate. In this study, we determined the atomic-level structure of Ab28)42 in an aqueous environment. We fused fragments of Ab, residues 10–24 (Ab10)24) or 28–42 (Ab28)42), to three positions in the C-terminal region of ribonuclease HII from a hyper-thermophile, Thermococcus kodakaraensis(Tk-RNase HII). | iFEBS Journal Structure of amyloid b fragments in aqueous environments Kazufumi Takano1 2 Shuji Endo1 Atsushi Mukaiyama1 Hyongi Chon1 Hiroyoshi Matsumura3 Yuichi Koga1 and Shigenori Kanaya1 1 Department of Materialand Life Science Osaka University Suita Japan 2 PRESTO Japan Science and Technology Agency JST Suita Japan 3 Department of Applied Chemistry Osaka University Suita Japan Keywords Alzheimer s disease crystal structure fusion protein conformational transition hyperthermophile protein Correspondence K. Takano Department of Material and Life Science Osaka University and PRESTO Japan Science and Technology Agency JST 2-1 Yamadaoka Suita Osaka 565-0871 Japan Tel Fax 81 6 6879 4157 E-mail ktakano@ Received 22 August 2005 revised 12 October 2005 accepted 7 November 2005 doi Conformational studies on amyloid b peptide Ab in aqueous solution are complicated by its tendency to aggregate. In this study we determined the atomic-level structure of Ab28_42 in an aqueous environment. We fused fragments of Ab residues 10-24 Abio_24 or 28-42 Ab28_42 to three positions in the C-terminal region of ribonuclease HII from a hyperthermophile Thermococcus kodakaraensis Tk-RNase HII . We then examined the structural properties in an aqueous environment. The host protein Tk-RNase HII is highly stable and the C-terminal region has relatively little interaction with other parts. CD spectroscopy and thermal denaturation experiments demonstrated that the guest amyloidogenic sequences did not affect the overall structure of the Tk-RNase HII. Crystal structure analysis of Tk-RNase HII1_197-Ab28_42 revealed that Ab28_42 forms a b conformation whereas the original structure in Tk-RNase HII1 _213 was a helix suggesting b-structure formation of Ab28_42 within full-length Ab in aqueous solution. Ab28_42 enhanced aggregation of the host protein more strongly than Ab10_24. These results and other reports suggest that after proteolytic .