Cross-Linking and Amyloid Formation by N- and C-Terminal Cysteine Derivatives of Human Apolipoprotein C-II

详细信息    查看全文

• 作者：Chi L. L. Pham ; Danny M. Hatters ; Lynne J. Lawrence ; and Geoffrey J. Howlett
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：December 3, 2002
• 年：2002
• 卷：41
• 期：48
• 页码：14313 - 14322
• 全文大小：606K
• 年卷期：v.41,no.48(December 3, 2002)
• ISSN：1520-4995

文摘

We have investigated the effect of disulfide cross-linking on amyloid formation by humanapolipoprotein (apo) C-II. Three derivatives of apoC-II were generated by inserting a cysteine residue oneither the N-terminus (C_N-apoC-II), C-terminus (C_C-apoC-II), or both termini (C_NC_C-apoC-II). Underreducing conditions, all derivatives formed amyloid with a fibrous ribbon morphology similar to that ofwild-type apoC-II. Under oxidizing conditions, C_N- and C_NC_C-apoC-II formed a highly tangled networkof fibrils, suggesting that the addition of an N-terminal cysteine to apoC-II promotes interfibril disulfidecross-links. Fibrils formed by C_C-apoC-II under oxidizing conditions were closely packed but less tangledthan fibrils formed by the C_N and C_NC_C derivatives. The frequency of closed ring structures was morethan doubled for C_C-apoC-II compared to wild-type apoC-II. The kinetics of fibril formation by all cysteinederivatives was markedly enhanced under oxidizing conditions, suggesting that disulfide cross-linkingpromotes amyloid formation. Substoichiometric levels of preformed C_N- and C_C-apoC-II dimers accelerateamyloid formation by wild-type apoC-II. These data suggest that the N- and C-termini of apoC-II areclose together in the amyloid fibril such that covalent cross-linking of either the N or C end of apoC-IIpromotes nucleation and the "seeding" of fibril growth.