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J. Cell Biol.,
Volume 142, Number 4, August 24, 1998 989-1000
* Department of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan and Mechanisms that regulate the movement of a
membrane spanning protein band 3 in erythrocyte
ghosts were investigated at the level of a single or small
groups of molecules using single particle tracking with
an enhanced time resolution (0.22 ms). Two-thirds of
band 3 undergo macroscopic diffusion: a band 3 molecule is temporarily corralled in a mesh of 110 nm in diameter, and hops to an adjacent mesh an average of every 350 ms. The rest (one-third) of band 3 exhibited
oscillatory motion similar to that of spectrin, suggesting
that these band 3 molecules are bound to spectrin. When the membrane skeletal network was dragged and
deformed/translated using optical tweezers, band 3 molecules that were undergoing hop diffusion were displaced toward the same direction as the skeleton. Mild
trypsin treatment of ghosts, which cleaves off the cytoplasmic portion of band 3 without affecting spectrin, actin, and protein 4.1, increased the intercompartmental
hop rate of band 3 by a factor of 6, whereas it did not
change the corral size and the microscopic diffusion
rate within a corral. These results indicate that the cytoplasmic portion of band 3 collides with the membrane
skeleton, which causes temporal confinement of band 3 inside a mesh of the membrane skeleton.
Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo 153-0041, Japan
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