Structure-function relationships in side chain lactam cross-linked peptide models of a conserved N-terminal domain of apolipoprotein E.
Structure-function relationships in side chain lactam cross-linked peptide models of a conserved N-terminal domain of apolipoprotein E.
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载脂蛋白 E 保守 N 末端结构域的侧链内酰胺交联肽模型中的结构-功能关系。
DOI：
10.1021/bi980482f
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Meredith,SC
中科院分区：
文献类型：
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作者：
Benzinger,TL;Braddock,DT;Dominguez,SR;Burkoth,TS;Miller-Auer,H;Subramanian,RM;Fless,GM;Jones,DN;Lynn,DG;Meredith,SC
生物活性多肽在溶液中有多种构象，但在脂质表面和与受体相互作用时具有明确的构象。我们使用侧链内酰胺交联剂稳定载脂蛋白E保守的N-末端结构域(括号中的交链周期性)的下列多肽模型中的二级结构：I，H2N-GQTLSEQVQEELLSSQVTQELRAG-COOH(无)；III，H2N-GDTLKEQVQEELLSEQVKDELKAG-COOH(I至I+3)；IV，H2N-GQDLSEKVQEELLESQVKDELLKAG-COOH(I至I+4)；Iva，H2 N-GQDLSEKEQLSEQVKELLLAG-COOH(I至4)(序列上方的内酰胺，下方的盐桥)。我们以前证明了[Luo等人(1994年)生物化学33,12367−12377；布拉多克等人(1996年)生物化学35,13975−13984]，肽III包含I和I+3侧链之间的内酰胺交联链，通过低密度脂蛋白受体以外的受体增强低密度脂蛋白的特异性结合。溶液中的多肽III由两个短的α螺旋组成，由一个非α螺旋段连接。在这里，我们检验了这样的假设，即由肽III模拟的结构域是构象开关的一个对极。为了模拟开关的另一个对极，我们在多肽III中引入了两个策略性修饰来研究该结构域中的结构和功能关系：(1)内酰胺交联链的间距被改变(在多肽IV和IVA中从I变为I+4)和(2)多肽IV和IVA在多肽III中可能的末端-封端相互作用的位置包含两个可选序列。2D-−确定多肽IV的结构在其全长为α螺旋。尽管结构有序程度显著，但肽IV在生物学上是无效的。相比之下，肽III和可能的IVA包含α螺旋的中央中断，这似乎是生物活性所必需的。这些和其他研究支持这样的假设，即该结构域是一个构象开关，在一定程度上它模拟载脂蛋白E本身，可能调节载脂蛋白E与其各种受体之间的相互作用。
Bioactive peptides have multiple conformations in solution but adopt well-defined conformations at lipid surfaces and in interactions with receptors. We have used side chain lactam cross-links to stabilize secondary structures in the following peptide models of a conserved N-terminal domain of apolipoprotein E (cross-link periodicity in parentheses): I, H2N-GQTLSEQVQEELLSSQVTQELRAG-COOH (none); III, H2N-GDTLKEQVQEELLSEQVKDELKAG-COOH (i to i+ 3); IV, H2N-GQDLSEKVQEELLESQVKDELLKAG-COOH (i to i+ 4); IVa, H2N-GQDLSEKVQEELLSEQVKDELLKAG-COOH (i to i+ 4)(lactams above the sequence, potential salt bridges below the sequence). We previously demonstrated [Luo et al.(1994) Biochemistry 33, 12367− 12377; Braddock et al.(1996) Biochemistry 35, 13975− 13984] that peptide III, containing lactam cross-links between the i and i+ 3 side chains, enhances specific binding of LDL via a receptor other than the LDL-receptor. Peptide III in solution consists of two short α helices connected by a non α helical segment. Here we examine the hypothesis that the domain modeled by peptide III is one antipode of a conformational switch. To model another antipode of the switch, we introduced two strategic modifications into peptide III to examine structure− function relationships in this domain:(1) the spacing of the lactam cross-links was changed (i to i+ 4 in peptides IV and IVa) and (2) peptides IV and IVa contain the two alternative sequences at a site of a possible end-capping interaction in peptide III. The structure of peptide IV, determined by 2D-NMR, is α helical across its entire length. Despite the remarkable degree of structural order, peptide IV is biologically inactive. In contrast, peptides III and possibly IVa contain a central interruption of the α helix, which appears necessary for biological activity. These and other studies support the hypothesis that this domain is a conformational switch which, to the extent that it models apolipoprotein E itself, may modulate interactions between apo E and its various receptors.