Benetollo C, Lambert G, Talussot C, Vanloo E, Cauteren T V, Rouy D, Dubois H, Baert J, Kalopissis A, Denèfle P, Chambaz J, Brasseur R, Rosseneu M
CJF INSERM 9508, Institut des Cordeliers, Paris, France.
Eur J Biochem. 1996 Dec 15;242(3):657-64. doi: 10.1111/j.1432-1033.1996.0657r.x.
Human apolipoprotein A-II (apo A-II) consists of three potential amphipathic helices of 17 residues each, which contribute to the lipid-binding properties of this apolipoprotein. The conformation and lipid-binding properties of these peptides, either as single-helix or as two-helix peptides, were investigated by turbidity, fluorescence, electron-microscopy and circular-dichroism measurements, and are compared in this article. The lipid affinity of shorter C-terminal segments of apo A-II was compared with those of the single-helix or two-helix peptides, to define the minimal peptide length required for stable complex formation. The properties of the apo-A-II-(13-48)-peptide were further compared with those of the same segment after deletion of the Ser31 and Pro32 residues, because the deleted apo-A-II-(13-30)-(33-48)-peptide, is predicted to form a long uninterrupted helix. The single helices of apo A-II could not form stable complexes with phospholipids, and the helix-turn-helix segment spanning residues 13-48 was not active either. The apo-A-II-(37-77)-peptide and the apo-A-II-(40-73)-peptide could form complexes with lipids, which appear as discoidal particles by negative-staining electron microscopy. The shortest C-terminal domain of apo A-II able to associate with lipids to form stable complexes was the apo-A-II-(40-73)-peptide, which consisted of the C-terminal helix, a beta-turn and part of the preceding helix. The shorter apo-A-II-(49-77)-peptide, and the helical apo-A-II-(13-30)-(33-48)-peptide, could also associate with phospholipids. The complexes formed were, however, less stable, as they dissociated outside the transition temperature range of the phospholipid. These data suggest that the C-terminal pair of helices of apo A-II, which is the most hydrophobic pair, is responsible for the lipid-binding properties of the entire protein. The N-terminal pair of helices of apo A-II at residues 13-48 does not associate tightly with lipids. The degree of internal similarity and the cooperativity between the helical segments of apo A-II is thus less pronounced than in apo A-I or apo A-IV. The N-terminal and C-terminal domains of apo A-II appear to behave as two distinct entities with regard to lipid-protein association.
人载脂蛋白A-II（apo A-II）由三个潜在的两亲性螺旋组成，每个螺旋含17个残基，这些螺旋对该载脂蛋白的脂质结合特性有贡献。通过浊度、荧光、电子显微镜和圆二色性测量研究了这些肽段作为单螺旋或双螺旋肽段时的构象和脂质结合特性，并在本文中进行了比较。比较了apo A-II较短C末端片段与单螺旋或双螺旋肽段的脂质亲和力，以确定形成稳定复合物所需的最小肽段长度。将apo-A-II-(13-48)-肽段与缺失Ser31和Pro32残基后的相同片段的特性进行了进一步比较，因为预测缺失的apo-A-II-(13-30)-(33-48)-肽段会形成一个长的不间断螺旋。apo A-II的单螺旋不能与磷脂形成稳定的复合物，跨越残基13-48的螺旋-转角-螺旋片段也没有活性。apo-A-II-(37-77)-肽段和apo-A-II-(40-73)-肽段可以与脂质形成复合物，通过负染色电子显微镜观察这些复合物呈现为盘状颗粒。apo A-II能够与脂质结合形成稳定复合物的最短C末端结构域是apo-A-II-(40-73)-肽段，它由C末端螺旋、一个β转角和前一个螺旋的一部分组成。较短的apo-A-II-(49-77)-肽段以及螺旋状的apo-A-II-(13-30)-(33-48)-肽段也可以与磷脂结合。然而，形成的复合物稳定性较差，因为它们在磷脂的转变温度范围之外会解离。这些数据表明，apo A-II的C末端螺旋对是最疏水的一对螺旋，并负责整个蛋白质的脂质结合特性。apo A-II在残基13-48处的N末端螺旋对与脂质的结合不紧密。因此，apo A-II螺旋段之间的内部相似程度和协同性不如apo A-I或apo A-IV明显。就脂质-蛋白质结合而言，apo A-II的N末端和C末端结构域似乎表现为两个不同的实体。
