Andree H A, Stuart M C, Hermens W T, Reutelingsperger C P, Hemker H C, Frederik P M, Willems G M
Cardiovascular Research Institute Maastricht, University of Limburg, The Netherlands.
J Biol Chem. 1992 Sep 5;267(25):17907-12.
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.
1985年，我们分离出一种新的血管抗凝蛋白VACα，即现在所称的膜联蛋白V，它对磷脂具有高结合亲和力（解离常数Kd小于10^(-10) M）。其抗凝作用归因于凝血因子从磷脂膜上被置换下来。本研究表明，膜联蛋白V对凝血酶原酶活性的抑制作用强烈依赖于膜表面的曲率和钙浓度。对于由20%磷脂酰丝氨酸和80%磷脂酰胆碱组成的小囊泡，凝血酶原酶活性被抑制一半以及膜联蛋白V与之结合一半时，需要2 - 3 mM钙。对于大囊泡和平面双层膜，抑制凝血酶原酶活性和脂质结合所需的钙要少得多。膜联蛋白V与大囊泡和平面双层膜结合一半时，分别在0.7 mM和0.2 mM钙浓度下发生。这似乎证实了置换模型。然而，凝血因子的置换被证明是不完全的，因子Xa、Va和凝血酶原的表面残余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与大囊泡结合会导致平面小面形成，表明形成了大片聚集的膜联蛋白V。显然，钙促进了这些二维阵列的形成，而高表面曲率则阻碍了其形成。据推测，膜联蛋白V对凝血酶原酶活性的完全抑制（大于99%）是由于覆盖在膜上的膜联蛋白V刚性片层中凝血酶原和因子Xa的横向流动性降低所致。
