Svoboda K, Mitra P P, Block S M
Rowland Institute for Science, Cambridge, MA 02142.
Proc Natl Acad Sci U S A. 1994 Dec 6;91(25):11782-6. doi: 10.1073/pnas.91.25.11782.
We studied fluctuations in the displacement of silica beads driven by single molecules of the motor protein kinesin, moving under low mechanical loads at saturating ATP concentrations. The variance in position was significantly smaller than expected for the case of stepwise movement along a regular lattice of positions with exponentially distributed intervals. The small variance suggests that two or more sequential processes with comparable reaction rates dominate the biochemical cycle. The low value is inconsistent with certain recently proposed thermal ratchet models for motor movement as well as with scenarios where the hydrolysis of a single ATP molecule leads to a cluster of several steps. Fluctuation analysis is a potential powerful tool for studying kinetic behavior whenever the output of a single enzyme can be monitored.
我们研究了在饱和ATP浓度下，在低机械负载下移动的驱动蛋白单个分子驱动的二氧化硅珠位移的波动情况。位置的方差明显小于沿具有指数分布间隔的规则位置晶格进行逐步移动的情况所预期的值。小方差表明两个或更多具有可比反应速率的连续过程主导了生化循环。该低值与最近提出的某些用于马达运动的热棘轮模型以及单个ATP分子水解导致一系列几步的情况不一致。每当可以监测单个酶的输出时，波动分析都是研究动力学行为的潜在有力工具。
