Observation of individual microtubule motor steps in living cells with endocytosed quantum dots |
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Authors: | Nan Xiaolin Sims Peter A Chen Peng Xie X Sunney |
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Institution: | Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA. |
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Abstract: | We report the observation of individual steps taken by motor proteins in living cells by following movements of endocytic vesicles that contain quantum dots (QDs) with a fast camera. The brightness and photostability of quantum dots allow us to record motor displacement traces with 300 micros time resolution and 1.5 nm spatial precision. We observed individual 8 nm steps in active transport toward both the microtubule plus- and minus-ends, the directions of kinesin and dynein movements, respectively. In addition, we clearly resolved abrupt 16 nm steps in the plus-end direction and often consecutive 16 nm and occasional 24 nm steps in minus-end directed movements. This work demonstrates the ability of the QD assay to probe the operation of motor proteins at the molecular level in living cells under physiological conditions. |
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