Clustering of lipid-bound annexin V may explain its anticoagulant effect.
Clustering of lipid-bound annexin V may explain its anticoagulant effect.
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DOI：
10.1016/s0021-9258(19)37128-5
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发表时间：
1992-09
期刊：
影响因子：
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通讯作者：
Harry A M Andrees;Marc C. A. Stuart;Wim Th Hermenss;Chris P M Reutelingspergerll;H. Coenraad Hemkern;Peter M Frederikp;George M Willemss
中科院分区：
文献类型：
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作者：
Harry A M Andrees;Marc C. A. Stuart;Wim Th Hermenss;Chris P M Reutelingspergerll;H. Coenraad Hemkern;Peter M Frederikp;George M Willemss
1985年，我们分离出一种新的血管抗凝蛋白VAC α，现在称为膜联蛋白V，对磷脂具有高结合亲和力（Kd小于10（-10）M）。其抗凝作用是由于从磷脂膜上置换凝血因子。本研究表明，凝血酶原酶活性的抑制膜联蛋白V强烈依赖于膜表面的曲率和钙离子浓度。凝血酶原酶对膜联蛋白V的半最大抑制和膜联蛋白V与由20%磷脂酰丝氨酸和80%磷脂酰胆碱组成的小囊泡的结合需要2-3 mM钙。对于大囊泡和平面双层，抑制凝血酶原酶和脂质结合所需的钙相当少。膜联蛋白V与大囊泡和平面双层的半最大结合分别发生在0.7和0.2 mM钙。这似乎证实了位移模型。然而，凝血因子的置换被证明是不完全的，因子Xa、Va和凝血酶原的残留表面浓度足以有效产生凝血酶。冷冻电子显微镜显示，膜联蛋白V结合到大的囊泡引起的平面刻面，表明形成大片的聚集膜联蛋白V。显然，这些二维阵列的形成是促进钙和阻碍高表面曲率。据推测，膜联蛋白V对凝血酶原酶活性的完全抑制（大于99%）是由覆盖膜的膜联蛋白V刚性片层中凝血酶原和因子Xa的侧向移动性降低引起的。
In 1985 we isolated a new vascular anticoagulant protein VAC alpha, now called annexin V, with a high binding affinity (Kd less than 10(-10) M) for phospholipids. Its anticoagulant effect was attributed to displacement of coagulation factors from the phospholipid membrane. The present study demonstrates that the inhibition of prothrombinase activity by annexin V strongly depends on the curvature of the membrane surface and on the calcium concentration. Half-maximal inhibition of prothrombinase on and binding of annexin V to small vesicles, composed of 20% phosphatidylserine and 80% phosphatidylcholine, requires 2-3 mM calcium. With large vesicles and planar bilayers considerably less calcium is required for inhibition of prothrombinase and for lipid binding. Half-maximal binding of annexin V to large vesicles and to planar bilayers occurs at 0.7 and 0.2 mM calcium, respectively. This seemingly confirms the displacement model. The displacement of coagulation factors, however, proved to be incomplete, with residual surface concentrations of factors Xa, Va, and prothrombin sufficient for effective production of thrombin. Cryoelectron microscopy revealed that annexin V binding to large vesicles caused planar facets, indicating the formation of large sheets of clustered annexin V. Apparently, the formation of these two-dimensional arrays is promoted by calcium and hampered by high surface curvature. It is speculated that the complete inhibition (greater than 99%) of prothrombinase activity by annexin V is caused by the reduced lateral mobility of prothrombin and factor Xa in rigid sheets of annexin V covering the membrane.