The Journal of Cell Biology, Vol 106, 133-140, Copyright © 1988 by The Rockefeller University Press
Isolation of a sixth dynein subunit adenosine triphosphatase of Chlamydomonas axonemes
G Piperno
Rockefeller University, New York 10021.
This study of the axoneme led to the identification of a previously unknown
adenosine triphosphatase (ATPase), which is likely a major component of
inner dynein arms. The ATPase was isolated from a soluble fraction of
axonemes obtained from pf 28, a Chlamydomonas mutant lacking the outer
dynein arms. The activity hydrolyzed up to 2.3 mumol of ATP.min-1.mg-1 of
protein (at pH 7.2, in the presence of both Ca++ and Mg++), had a
sedimentation coefficient of 11S in sucrose gradient, and cosedimented with
four polypeptides of apparent molecular weight 325,000, 315,000 140,000,
and 42,000. Several arguments indicate that the new ATPase is a component
of the inner dynein arms. Three or four polypeptides cosedimenting with the
activity belong to a group of axonemal components that are deficient in the
axonemes of pf 23 and pf 30, two mutants that display different levels of
inner dynein arm deficiency. The 42,000 component is axonemal actin, a
subunit of two other inner dynein ATPases. The two polypeptides of
molecular weight greater than 300,000 have electrophoretic mobility similar
to that of high molecular weight components of outer and inner dynein arms.
In spite of some similarities each ATPase isolated from inner or outer arms
is composed of a different set of polypeptides. Different ATPases may be
required for the modulation of localized sliding of adjacent outer double
microtubules in the axoneme.
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