Microfilament Motors
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Skeletal
(Striated)
Muscle
Z
+
-
-
+
+
-
-
+
+
+
Sliding filament contraction
M
Z
animation
AFM
Myosin II Structure
Control by
Troponin/Tropomyosin
Ca++
The Swinging Lever Arm
+ ATP
Minus
->ADP+Pi
- Pi, ADP
Plus
Muscle Myosin (II)
animation
Plus
Minus
animation
Making its moves
Minus
Plus
GFP-Myosin in
a
Cardiomyocyte
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video
Stress-Mediated Orientation
The Myosin Family Tree (24 and growing)
Myosin Alignments
From the Fold (the Ur-Motor?)
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Myosin
class
Animals Fungi
Dictyostelium
I
X
X
X
II
X
X
X
III
X
IV
Apicom
plexans
Kinetoplastids
X
*
V
X
VI
X
?
VII
X
?
X
VIII
?
X
X
IX
X
X
*
XI
XII
Plants
Myosin
Classes
X
*
XIII
*
XIV
X
XV
X
XVI
*
XVII
*
XVIII
X
XIX
*
XX
*
XXI
X
XXII
X
XXIII
X
XIV
X
X = present
* = limited
Saccharomyces cerevisiae
Gene
Myosin Involved in
class
function
Mutant phenotype
MYO1 class II
cell division
myo1=forms cell chains
MYO2 class V
polarized
growth
myo2 = can't bud
MYO3 class I
endocytosis
myo3,5 double mutant defective in endocytosis
MYO4 class V
cell fate
myo4 = mother/daughter mating type switching
defective
MYO5 class I
endocytosis
myo3,5 double mutant defective in endocytosis
39 myosins in the human genome, and counting!
Myosins
Everywhere!
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video
In Vitro Motor
Assays
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Myo IXb is a plusend directed motor
Myo II
(because the polarity
marked microfilament,
red at the plus end, moved
in a minus-end direction
over the motor)
video
MyoMotors, Inc.
Differential localization
Myosin I
Myosin II
Myo V
Stepping
out
Melanosome
Rab27
Melanophilin
37 nm per step
Plus
74 nm per stride
37nm
A flip-book animation
Barbed-end myosins
move in plus-end
directions
Pointed-end myosins
move in minus-end
directions
Running in
reverse
Myosin VI has an insertion in
the converter region that
changes its lever arm
Myo VI
and
Myo V
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Can you hear
me now?
Myosin VI localization
Myosin
Mutations
Create Deafness
Normal stereociliary bundles in the cochlea
Myosin XVa-GFP
are disorganized in a Myosin VIIa waltzer mutant
5 um
Phosphoinositide
lipid binding
domains
MyoX-GFP
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video
microfilaments