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J. Cell Biol.,
Volume 141, Number 7, June 29, 1998 1551-1561
Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, 69978 Tel-Aviv, Israel
Cell membrane fluctuations (CMF) of human erythrocytes, measured by point dark field microscopy, were shown to depend, to a large extent, on intracellular MgATP (Levin, S.V., and R. Korenstein. 1991. Biophys. J. 60:733-737). The present study extends that investigation and associates CMF with F-actin's ATPase activity. MgATP was found to reconstitute CMF in
red blood cell (RBC) ghosts and RBC skeletons to
their levels in intact RBCs, with an apparent Kd of 0.29 mM. However, neither non-hydrolyzable ATP analogues (AMP-PNP, ATP
S) nor hydrolyzable ones
(ITP, GTP), were able to elevate CMF levels. The inhibition of ATPase activity associated with the RBC's
skeleton, carried out either by the omission of the
MgATP substrate or by the use of several inhibitors
(vanadate, phalloidin, and DNase I), resulted in a
strong decrease of CMF. We suggest that the actin's
ATPase, located at the pointed end of the short actin
filament, is responsible for the MgATP stimulation of
CMF in RBCs.
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