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SEM
75 mM KCl
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Communication between Flagellar Outer and Inner Dynein Arms
Toshiyuki Oda, Toshiki Yagi, Masahide Kikkawa
Dept. Cell Biology, Univ. Tokyo, Grad. Sch. Medicine
The beating motion of cilia and flagella is driven by two rows of dynein arms:
the outer dynein arms ODA and the inner dynein arms IDA. The ODAs are
required to generate the normal beat frequency and the IDAs are responsible for
the amplitude of the waveform. Although structural connections between the ODA
and the IDA have been observed by cryoelectron tomography, the functional
communication between the two species of the dynein arms has not been
elucidated. In this study, we investigated the roles of the two intermediate chains
IC1 and IC2 of Chlamydomonas ODA. We located the positions of the termini
of the ICs within the ODAmicrotubule complexes by biotinstreptavidin labeling
and cryoelection microscopy. It is noteworthy that the location of the Nterminus
of IC2 is close to the previously observed ODAIDA linker. The biotintag added
to the Nterminus of IC2 reduced the amplitude of the beating by half while the
beat frequency was not decreased. These results suggest the Nterminus of IC2
mediates the communication between the ODA and the IDA.
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A novel protein complex required for the formation of microtubule
square lattice in green tree frog sperm
Toshiki Yagi 1 , Hiroshi Kubota 2 , Masahide Kikkawa 1
1
Grad. Sch. Medicine, Univ. Tokyo, 2 Grad. Sch. Science, Kyoto Univ.
Fertilization of the green tree frog occurs in the viscous environment of a foam
nest laid on the vegetation. The sperm cell moves through viscous media by
spinning of the spiral head with flagellar bending movements. Previous EM
analysis showed that the flagellum is composed of a pair of axonemes surrounded
by a regular square lattice of hundreds of satellite microtubules MTs. To
understand how the unique MT lattice structure forms, here we purified MT
bundling proteins from the flagella and examined the properties of the proteins.
Sperm cells were fragmented and fractionated into heads and short flagella by
sonication and centrifugation. Proteins with MT bundling activity was purified
from high salt extract of demembranated flagella by gel filtration chromatography.
This fraction contained six proteins with the molecular size of 3545 kDa. All the
proteins were precipitated together by MTpelleting assay, suggesting that they
form a complex with MT. EM analysis on salt extracted sperm showed that the
flagella lost crosslink structures in the MT lattice. Taken together, we suggest that
the protein complex constitutes the crosslink structure required for the MT lattice
formation.
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LH/FSH
LH/FSH
TGN38 trans γtubulin
cistrans
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Mitochondria form continuous intracellular networkstructures: a
study visualized by highresolution scanning electron microscopy
Tomonori Naguro, Hironobu Nakane, Sumire Inaga
Division of Genome Morphology, Fac. Medicine, Tottori Univ.
The mitochondria of rat olfactorybulb granule cells in vivo cells within the
tissue formed a continuous network of various shapes in each cell. On the basis
of the morphological characteristics, these mitochondrial networks were roughly
classified into four groups: Type1: Mitochondrial networks are composed of
a single branched tubule of almost uniform thickness, 250300 nm. Type2:
Distinguished by thickness, mitochondrial networks have two kinds of tubules:
about 250350 nm and 100 nm across, respectively. Type3: Mitochondrial
networks are composed of two parts; a globular part around 1.0 μm in diameter
and a filamentous part about 45100 nm across. Type4: Highly complex
mitochondrial networks consisting of elements those vary in shape.
The significance of this morphological diversity of mitochondrial networks
is discussed referring to recent studies with other means, notably light and
transmissionelectron microscopy while considering the advantages and
disadvantages of scanning electron microscopy methods employed for this here.
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Mt
C57BL/6
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2.5
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5 Mt
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