Veeraraghavan S, Baleja J D, Gilbert G E
Department of Biochemistry, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111, USA.
Biochem J. 1998 Jun 1;332 ( Pt 2)(Pt 2):549-55. doi: 10.1042/bj3320549.
A 21 residue peptide from the C2 domain of the antihaemophilic factor VIII competes with factor VIII for membrane-binding sites in vitro. Here, we provide the structure and topography of the peptide in solution, on dodecylphosphocholine (DPC) micelles, determined using 1H-NMR spectroscopy. The peptide assumes an amphipathic structure comprising an extended N-terminal region and a C-terminal helix. The average root-mean-square deviation is 0.7+/-0.2 A for the superimposition of the backbone atoms of Ile6 to Arg18 on the lowest energy structure. Whereas the backbone conformation is similar to that in SDS micelles, the Trp11 side-chain orientation is dramatically changed. The indole ring is nearly parallel to the peptide backbone in SDS micelles but perpendicular in DPC micelles. Further, pKa values of the two histidines change by more than 1 pH unit in SDS relative to DPC, which localizes the imidazole rings to the interfacial region. Line-broadening induced by spin-labelled phosphatidylcholine shows that most of the amino acid side-chains that penetrate the DPC micelle are hydrophobic. Thus, the long axis of the peptide lies parallel to the micelle surface and the hydrophobic face of the alpha-helix provides hydrophobic membrane interaction. The large chemical shift changes shown by Trp11 and N-terminal amino acid residues in SDS relative to DPC indicate that this region may be involved in membrane phospholipid recognition. 1H-NMR assignments, CD spectra, one-dimensional 1H-NMR spectra, chemical-shift analysis and nuclear Overhauser effect information are reported in Supplementary Publication SUP 50184 (11 pages), which has been deposited at the British Library Document Supply Centre, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K, from whom copies can be obtained according to the terms indicated in Biochem. J. (1997) 321, 8.
来自抗血友病因子VIII C2结构域的一个21个残基的肽段在体外与因子VIII竞争膜结合位点。在此，我们利用1H-NMR光谱法提供了该肽段在溶液中、在十二烷基磷酸胆碱（DPC）胶束上的结构和拓扑结构。该肽段呈现出一种两亲结构，包括一个伸展的N端区域和一个C端螺旋。对于Ile6至Arg18的主链原子在最低能量结构上的叠加，平均均方根偏差为0.7±0.2埃。虽然主链构象与在SDS胶束中的相似，但Trp11侧链的取向发生了显著变化。在SDS胶束中吲哚环几乎与肽主链平行，而在DPC胶束中则垂直。此外，相对于DPC，两个组氨酸的pKa值在SDS中变化超过1个pH单位，这将咪唑环定位在界面区域。自旋标记磷脂酰胆碱诱导的线宽展宽表明，穿透DPC胶束的大多数氨基酸侧链是疏水的。因此，肽段的长轴与胶束表面平行，α螺旋的疏水面提供疏水膜相互作用。相对于DPC，Trp11和N端氨基酸残基在SDS中显示出大的化学位移变化，表明该区域可能参与膜磷脂识别。1H-NMR归属、CD光谱、一维1H-NMR光谱、化学位移分析和核Overhauser效应信息在补充出版物SUP 50184（11页）中有报道，该出版物已存放在英国西约克郡韦瑟比波士顿温泉市的大英图书馆文献供应中心，邮编LS23 7BQ，可根据《生物化学杂志》（1997年）321卷8期所示条款从该中心获取复印件。
