(2) Single molecule capture, manipulation and force measurement of protein molecules

Kazuo KITAMURA¹, Atsuko IWANE², Toshio YANAGIDA^1,2 and Makio TOKUNAGA (¹Single Molecule Processes Project, ICORP, JST, ²Department of Physiology I, Osaka University Medical School)

　We have developed a new instrument to capture and directly manipulate individual molecules using a scanning probe. A single myosin head molecule (myosin subfragment-1, S1) was captured onto the tip of a scanning microprobe using a flexible glass microprobe, and manipulated with subnanometer resolution. Single molecule was confirmed by examining in the fluorescence microscopy at the same time using objective-type TIRFM. Movements and forces resulting from the interaction of a captured single S1 molecule with actin filaments were measured. Our data are consistent with the unitary mechanical step during sliding along an actin filament of ~5.3 nm, but groups of 2 to 5 rapid steps in succession often produce displacements of ~11 to ~30 nm. The instances of multiple stepping are produced by single heads during one biochemical cycle of ATP hydrolysis. The results proves that the loose coupling mechanism is right. For details, see Ref. 2.