Mechanical properties of inner-arm dynein-f (dynein I1) studied with in vitro motility assays
Norito Kotani 1, Hitoshi Sakakibara 2, Stan A Burgess 3, Hiroaki Kojima 2 and Kazuhiro Oiwa 2*
1 Graduate School of Life Science, University of Hyogo
2 Kobe Advanced ICT Research Center
3 Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds
* To whom correspondence should be addressed. E-mail: oiwa{at}nict.go.jp.
Submitted on November 27, 2006
Revised on January 4, 2007
Accepted on 6 April 2007
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Abstract |
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Inner-arm dynein-f of Chlamydomonas flagella is a heterodimeric dynein. We performed conventional in vitro motility assays showing that dynein-f translocates microtubules at the comparatively low velocity of about 1.2 µm/s. From the dependence of velocity upon the surface density of dynein-f, we estimate its duty ratio to be 0.6-0.7. The relation between microtubule landing rate and surface density of dynein-f are well fitted by the first-power dependence, as expected for a processive motor. At low dynein densities, progressing microtubules rotate erratically about a fixed point on the surface, at which a single dynein-f molecule is presumably located. We conclude that dynein-f has high processivity. In an axoneme, however, slow and processive dynein-f could impede microtubule sliding driven by other fast dyneins (e.g. dynein-c). To obtain insight into the in vivo roles of dynein-f, we measured the sliding velocity of microtubules driven by a mixture of dyneins -c and -f at various mixing ratios. The velocity is modulated as a function of the ratio of dynein-c in the mixture. This modulation suggests that dynein-f acts as a load in the axoneme, but force pushing dynein-f molecules forward seems to accelerate their dissociation from microtubules.
Key Words:
Chlamydomonas, axoneme, duty ratio, processivity, protein motor
