POTENTIAL-SENSITIVE RESPONSE MECHANISM OF DIS-C3-(5) IN BIOLOGICAL-MEMBRANES
POTENTIAL-SENSITIVE RESPONSE MECHANISM OF DIS-C3-(5) IN BIOLOGICAL-MEMBRANES
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DOI：
10.1007/bf01870706
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发表时间：
1986-01-01
影响因子：
2.4
通讯作者：
VERKMAN, AS
中科院分区：
文献类型：
--
作者：
CABRINI, G;VERKMAN, AS
The potential-sensitive response mechanism of 3,3''-dipropylthiodicarbocyanine iodide (diS-C3-(5)) was examined based on our previous model of diS-C3-(5) interaction with brush border membrane vesicles (BBMV) in the absence of a membrane potential. The model contained binding (6 msec), reorientation (30 msec), dimerization (< 10 nsec), and translocation (1 sec) reaction steps (Cabrini and Verkman, 1986. J. Membrane Biol. 90:163-175). Transmembrane potentials (.psi.) were induced in BBMV by K+ gradients and valinomycin. Steady-state diS-C3-(5) fluorescence (excitation 622 nm, emission 670 nm) increased linearly with .psi.. The reorientation and translocation reaction steps were resolved by the stopped-flow technique as a biexponential decrease in fluorescence following mixture of diS-C3-(5) with BBMV at varying .psi.. The fractional amplitude of the faster exponential increased from 0.36 to 0.73 with increasing .psi. (-17 to 87 mV); the time constant for the faster exponential (30-35 msec) was independent of .psi.. There were single exponential kinetics (0.5-1.5 sec) for diS-C3-(5) fluorescence response to a rapid (< 2 msec) change in .psi. in the absence of a diS-C3-(5) concentration gradient. These results, and similar findings in placental brush border vesicles, red cell vesicles, and phosphatidylcholine vesicles, support a translocation mechanism for diS-C3-(5) response, where induced membrane potentials drive diS-C3-(5) redistribution between sites at the inner and outer membrane leaflets, with secondary effects on diS-C3-(5) dimerization and solution/membrane partitioning. Fluorescence lifetime and dynamic depolarization measurements showed no significant change in diS-C3-(5) rotational characteristics or in the polarity of the dis-C3-(5) environment with changes in .psi.. Based on the experimental results, a mathematical model is developed to explain the quantitative changes in diS-C3-(5) fluorescence which accompany changes in .psi. at arbitrary dye/lipid ratios.
