Observation of individual microtubule motor steps in living cells with endocytosed quantum dots.
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.
Nan
Xiaolin
X
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Sims
Peter A
PA
Chen
Peng
P
Xie
X Sunney
XS
D045744:Cell Line, Tumor; D003593:Cytoplasm / Q000502:physiology / Q000648:ultrastructure; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D020409:Molecular Motor Proteins / Q000502:physiology* / Q000648:ultrastructure; D045663:Quantum Dots; D022161:Transport Vesicles / Q000502:physiology* / Q000648:ultrastructure
D020409:Molecular Motor Proteins