Caputo C B, Sobel I R, Sygowski L A, Lampe R A, Spreen R C
Department of Pharmacology, ICI Americas, Wilmington, Delaware 19897.
Arch Biochem Biophys. 1993 Nov 1;306(2):321-30. doi: 10.1006/abbi.1993.1518.
C-APP, a synthetic peptide corresponding to the C-terminal 20 amino acids of beta-amyloid precursor protein, forms amyloid fibrils in vitro. We investigated the effect of altering the C-APP sequence or deleting part of it on its ability to form amyloid fibrils. Substituting any single amino acid in the C-APP sequence with alanine did not prevent the formation of CAPP-like fibrils. Peptides with single or multiple substitutions that included T11, F14, F15, or Q19 showed reduced fibril-forming capacity while those with K1 and/or K13 replaced with alanine or glutamic acid showed enhanced capacity. When P10 or F14 was replaced with alanine, the fibrils were less congophilic than C-APP fibrils. All of the truncated peptides that were able to form fibrils contained at least 9 amino acids from the N-terminus of C-APP or amino acids 7-20 from the C-terminus. However, several peptides that met these criteria, but started at Q3 or contained only 2-4 amino acids C-terminal to P-10, failed to form many or typical fibrils. Peptides that contained the C-APP sequence plus 5-20 adjacent amino acids from the beta-amyloid precursor protein formed fibrils less readily than C-APP and most of the fibrils were not congophilic. The exception was CAPP-30, which formed moderate amounts of congophilic fibrils resembling C-APP fibrils morphologically. Therefore, proteolysis which releases C-APP from these peptides (except CAPP-30) would be predicted to enhance their amyloidogenicity. These results suggest that several features of C-APP peptide may be important in fibril formation. One of these features is the length of the peptide, with lengths of about 10, 20, or 30 amino acids, favoring fibril formation.
C-APP是一种与β-淀粉样前体蛋白C末端20个氨基酸相对应的合成肽，可在体外形成淀粉样纤维。我们研究了改变C-APP序列或删除其部分序列对其形成淀粉样纤维能力的影响。用丙氨酸替换C-APP序列中的任何单个氨基酸都不会阻止CAPP样纤维的形成。包含T11、F14、F15或Q19的单取代或多取代肽显示出降低的纤维形成能力，而那些K1和/或K13被丙氨酸或谷氨酸取代的肽显示出增强的能力。当P10或F14被丙氨酸取代时，这些纤维比C-APP纤维的刚果红亲和力更低。所有能够形成纤维的截短肽都包含至少9个来自C-APP N末端的氨基酸或来自C末端的7-20个氨基酸。然而，一些符合这些标准但从Q3开始或仅包含P-10 C末端2-4个氨基酸的肽未能形成许多或典型的纤维。包含C-APP序列加上β-淀粉样前体蛋白5-20个相邻氨基酸的肽比C-APP更不容易形成纤维，并且大多数纤维没有刚果红亲和力。例外的是CAPP-30，它形成了中等数量的刚果红亲和力纤维，在形态上类似于C-APP纤维。因此，预计从这些肽（CAPP-30除外）中释放C-APP的蛋白水解作用会增强它们的淀粉样生成能力。这些结果表明，C-APP肽的几个特征可能在纤维形成中很重要。其中一个特征是肽的长度，约10、20或30个氨基酸的长度有利于纤维形成。
