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J. Cell Biol.,
Volume 141, Number 6, June 15, 1998 1371-1381
Department of Anatomy and Cell Biology, Columbia University College of Physicians and Surgeons, New York,
New York 10032
Transfer of mitochondria to daughter cells
during yeast cell division is essential for viable progeny.
The actin cytoskeleton is required for this process, potentially as a track to direct mitochondrial movement
into the bud. Sedimentation assays reveal two different
components required for mitochondria-actin interactions: (1) mitochondrial actin binding protein(s)
(mABP), a peripheral mitochondrial outer membrane
protein(s) with ATP-sensitive actin binding activity,
and (2) a salt-inextractable, presumably integral, membrane protein(s) required for docking of mABP on the
organelle. mABP activity is abolished by treatment of
mitochondria with high salt. Addition of either the salt-extracted mitochondrial peripheral membrane proteins
(SE), or a protein fraction with ATP-sensitive actin-binding activity isolated from SE, to salt-washed mitochondria restores this activity. mABP docking activity
is saturable, resistant to high salt, and inhibited by pre-treatment of salt-washed mitochondria with papain.
Two integral mitochondrial outer membrane proteins, Mmm1p (Burgess, S.M., M. Delannoy, and R.E.
Jensen. 1994. J.Cell Biol. 126:1375-1391) and Mdm10p,
(Sogo, L.F., and M.P. Yaffe. 1994. J.Cell Biol. 126:1361-
1373) are required for these actin-mitochondria interactions. Mitochondria isolated from an mmm1-1 temperature-sensitive mutant or from an mdm10 deletion
mutant show no mABP activity and no mABP docking
activity. Consistent with this, mitochondrial motility in
vivo in mmm1-1 and mdm10
mutants appears to be
actin independent. Depolymerization of F-actin using
latrunculin-A results in loss of long-distance, linear
movement and a fivefold decrease in the velocity of mitochondrial movement. Mitochondrial motility in
mmm1-1 and mdm10
mutants is indistinguishable
from that in latrunculin-A-treated wild-type cells. We
propose that Mmm1p and Mdm10p are required for
docking of mABP on the surface of yeast mitochondria
and coupling the organelle to the actin cytoskeleton.
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