microfilament actin 1
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MICROFILAMENT ACTIN
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Microfilament
(thin filament)structure
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this
25nm
--- 7-8nm
G-actin
monomer
ATP
minus
plus
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MIKROFILAMEN
diameter 60 angstrom
consist of actin protein
molecule.
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Actin Filaments
Thinner, shorter and more flexible thanmicrotubules
Contains G-actin, and -actin Actin- most abundant intracellular
protein in most !u"ar#otic cells
Comprises $%& b# 'ei(ht of total cellprotein in muscle cells, $-5& in non-muscle cells
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G-actin and F-actin
G-actin) exists as a (lobular monomer
-actin) is a helical filamentous pol#mer of G-
actin subunits all oriented in the samedirection
*icrofilaments in a cell are constantl#
shrin"in( or (ro'in( in len(th
+undles and mesh'or"s of microfilaments
are formin( and dissolin( continuousl#
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A"tin merupa"an protein
(lobular, dalam bentu"monomer disebut a"tin G, #an(
dapat dira"it menadi filamen
ran("ap #an( disebut a"tin
A"tin mudah terurai menadimonomer-monomern#a dan
tera"it "embali menadi
mi"rofilamen
A"tin terlibat dalam proses-proses #an( teradi dalam sel
.sito"inesis, aliran plasma,
(era"an sel, (era"an mi"roili
intestinal, dsb/
Aktin GAktin F
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!namics of Actin Assem"l!
0ucleation- G-actin clumps into short,unstable oli(omers, 1-4 subunits lon(, and
acts as a stable nucleus, proteins include
the Arp21 complex .actin nucleator/ or bindin( nucleator) tandem-monomer-
bindin( nucleators3
!lon(ation phase- increases in len(thb# the addition of actin monomers to ./
end b# protein formin
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!namics of Actin Assem"l!
6tead#-6tate
The ends of actin filaments are in a stead#
state 'ith monomeric G-actin After their incorporation into a filament,
subunits slo'l# h#drol#e ATP and become
stable -actin
Protein profilin, 'hich catal#es AP to ATP
exchan(e and Acofilin, 'hich mediates
filament disassembl#
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Copyright (c) by W. H. Freeman and Company
Nucleation, Elongation, and the Steady-State
Figure 18-11
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FILAMEN AKTIN
iumpai seba(ai arin(-
arin( trimatra #an( "a"u,
"arena filamen a"tin
san(at teri"at den(an
protein pen(i"at silan(
.cros lin"in(/ Protein pen(i"at silan(
#an( ban#a" terdapat di
dalam sel #aitu filamin,#aitu suatu mole"ul
panan( dan lentur terdiri
dari dua rantai polipeptida
"embar
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All subunits in an actin filament point to'ardthe same direction of the filament !xhibits polarit#-actin subunit exposed to the
surroundin( solution is the .-/ end
The cleft that has contact 'ith the nei(hborin(actin subunit that is not exposed is the ./ end
Actin filaments (ro' faster at the ./ end than the.-/ end
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F-actin has structural and functional
polarity
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$9
Actin Filaments #artici#ate in a
$ariet! of cell functions% Anchora(e and moement of
membrane proteins- filaments are distributed in 1-dimensional
net'or"s throu(hout the cell
used as anchors 'ith in specialied cell
unctions
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Actin Filaments #artici#ate in a
$ariet! of cell functions% ormation of the structural core of
microilli
:n epithelial cells, help maintain shape ofthe cell surface
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MIKROILIo
Adala! ton"olan#ton"olan$er$entu% "ari &ang terdapat dipermu%aan sel' terutama sel!e(an
o )an"angn&a se%itar satumi%rometer' dan garis
tenga!n&a *0 nanometero +agian tenga! mi%ri,ili $erisi
se$er%as -lamen#-lamen a%tin&ang tersusun se"a"ar satuter!adap &ang lain' denganu"ung positifn&a mengara! %epermu%aan sel
o Filamen#-lamen terse$utdi!u$ung%an satu dengan &anglain ole! protein#proteinpengi%at &aitu -m$rin' ,ilin'
dan %omple%s calmodulin.
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Actin Filaments #artici#ate in a
$ariet! of cell functions% ;ocomotion of the cells
Achieed b# the force exerted b# actin
filaments b# pol#meriation at their (ro'in(ends
<sed in man# mi(ratin( cells, particularl#on transformed cells of inasie tumors
Cells extend processes from their surfaceb# pushin( the plasma membrane aheadof the (ro'in( actin filaments