Yoshimura T, Welti R, Helmkamp G M
Department of Biochemistry, University of Kansas Medical Center, Kansas City 66103.
Arch Biochem Biophys. 1988 Nov 1;266(2):299-312. doi: 10.1016/0003-9861(88)90262-7.
Phospholipid transfer protein catalyzes the transfer of phospholipids between bilayer membranes. A general model is developed for describing the kinetics of this process. While previous models derive detailed expressions only for the initial rate of transfer from donor to acceptor membranes, this model takes into account donor-to-donor, acceptor-to-acceptor, and acceptor-to-donor transfers, in addition to the usual donor-to-acceptor transfer. The apparent rate of transfer along any of these specific routes is given as the product of the total rate of transfer (the sum of the rates of transfer along all four routes) and a probability function uniquely defined for each route. The model explains adequately the effects of membrane concentration on phospholipid transfer activity as well as the consequences of varying membrane surface charge and size. Using bovine liver phosphatidylcholine transfer protein, the model is applied to the kinetic analysis of phosphatidylcholine transfer between two populations of small unilamellar vesicles. Rates of protein-catalyzed phosphatidylcholine transfer between vesicles with identical phosphatidic acid content (2 or 6 mol%) are determined experimentally as a function of total vesicle concentration to calculate apparent dissociation constants and maximum rates of transfer; apparent rates of transfer between various combinations of vesicles containing 2 or 6 mol% phosphatidic acid are then deduced from the derived velocity expression. Reasonably good agreement is seen between theoretical apparent rate-vesicle concentration relationships and those measured experimentally. The results support the general treatment of the kinetics of protein-mediated phospholipid transfer and permit an estimation of useful kinetic parameters.
磷脂转移蛋白催化磷脂在双层膜之间的转移。建立了一个通用模型来描述这一过程的动力学。虽然先前的模型仅推导了从供体膜到受体膜转移的初始速率的详细表达式，但该模型除了考虑通常的供体到受体的转移外，还考虑了供体到供体、受体到受体以及受体到供体的转移。沿着这些特定途径中任何一条的表观转移速率表示为总转移速率（沿着所有四条途径的转移速率之和）与为每条途径唯一定义的概率函数的乘积。该模型充分解释了膜浓度对磷脂转移活性的影响以及膜表面电荷和大小变化的后果。使用牛肝磷脂酰胆碱转移蛋白，该模型应用于两个小单层囊泡群体之间磷脂酰胆碱转移的动力学分析。实验测定了具有相同磷脂酸含量（2或6摩尔%）的囊泡之间蛋白质催化的磷脂酰胆碱转移速率作为总囊泡浓度的函数，以计算表观解离常数和最大转移速率；然后从推导的速度表达式中推导出含有2或6摩尔%磷脂酸的各种囊泡组合之间的表观转移速率。理论表观速率与囊泡浓度关系与实验测量结果之间存在合理的良好一致性。结果支持了对蛋白质介导的磷脂转移动力学的一般处理，并允许估计有用的动力学参数。
